Rozprawy doktorskie na temat „PVA Nanocomposite”

In this project, composite membranes containing nanoparticles of polydopamine PDA (dopamine polymer) will be manufactured and characterized in view of their use for the separation of CO2. Polysulfone will be used as a polymer matrix support while poly(vinyilalcohol) has been chosen as selective layer material. The work will first focus on the optimization of the manufacturing parameters of nano composite membranes and then on the influence of the integration of PDA nanoparticles in the polymeric support at different concentrations. The final objective is to test the material properties, with particular reference to the separation performances of the membranes produced, and critically comment on the results obtained.

The search for alternative energy generation methods requires development for new energy storage methods as well. The ability to use nanotechnology to achieve high surface area, which is correlated to increased energy storage, brought advancements in supercapacitor applications. Supercapacitors have the potential to charge and discharge quickly and hold as much energy as batteries and other chemical storage devices. By having a completely solid-state supercapacitor, problems with leakage and decay could be avoided. Supercapacitors were assembled from electrodes made by reducing graphene oxide in a computer disc drive and adhering two electrodes with composite electrolytes having various concentrations of PVA/CNT. Tests were performed on the completed supercapacitors, as well as the individual components. The analysis of the different concentrations of carbon nanotubes in PVA electrolytes showed the lowest resistivity for 0.5wt% CNT (294 Omega cm) and the highest specific capacitance for 1.0wt% CNT (123.5 F/g). This specific capacitance is a 27% improvement on an electrolyte without CNT. The electrolyte with pure PVA has similar capacitance to other solid-state supercapacitors in the literature. Electrolytes with higher percentages of CNT (0.5%) show higher resistivity because of the decreased carbon solubility or agglomerations. The final product supercapacitors, thin, flexible, and environmentally friendly, can be used in wide temperature ranges, and have a theoretically long lifespan. They can charge more quickly than batteries, and hold more energy than capacitors. This study shows promising enhancements in solid-state supercapacitors, making them an even more plausible replacement for batteries in the near future. The improvements made on the specific capacitance with the different electrolytes could lead to greater efficiency and lower cost in many unique applications requiring absence of liquid components.
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering

Ce travail est consacré à l‟étude de la stabilité photochimique de nanocomposites polymère / argile en vue de leur insertion dans un système multicouche organique / inorganique pour l‟encapsulation des cellules solaires organiques. L‟objectif est d‟obtenir des films de nanocomposites polymère / argile flexibles, transparents, pouvant être mis en oeuvre par voie liquide, et photochimiquement stables. Dans une première partie, la caractérisation de nanocomposites à base d‟alcool polyvinylique (PVA) a montré leur aptitude à être insérés dans un système multicouche, notamment en ce qui concerne les propriétés barrière aux gaz. L‟étude du comportement photochimique du PVA basée sur l‟identification des produits de dégradation a permis de proposer un mécanisme de photooxydation du PVA et de déterminer les effets du photovieillissement sur les propriétés du film (rugosité, perméabilité, transparence). L‟insertion de nanocharges lamellaires (Montmorillonite, Laponite ou Hydroxydes Doubles Lamellaires) dans le PVA induit des effets différents (prodégradant ou stabilisant) en fonction de la nature de l‟argile (naturelle ou synthétique). Cependant, lors d‟irradiations en absence d‟oxygène, le PVA et les nanocomposites PVA / argile sont très stables. Enfin, l‟encapsulation alternant couche inorganique SiOx et couche organique PVA ou nanocomposite PVA / argile, permet d‟atteindre les niveaux de perméation requis pour les cellules solaires organiques pour des applications nomades
This work was devoted to the study of the photochemical behavior of polymer / clay nanocomposites with the aim to use these nanocomposites in a multilayer organic / inorganic coating for organic solar cells encapsulation. The goal of this work was to obtain polymer / clay nanocomposite films that are flexible, transparent, which can be processed by solution, and that are photochemically stable. In the first part, the characterization of nanocomposites based on polyvinyl alcohol (PVA) has shown their ability to be inserted into a multilayer system, particularly for gas barrier properties. The study of the photochemical behavior of PVA with the identification of photodegradation products allows us to propose a photooxidation mechanism of PVA and to determine the effects of photoageing on the film properties (roughness, permeability, transparency). The insertion of lamellar nanofillers (Montmorillonite, Laponite or Layered Double Hydroxide) in PVA induces different effects (prodegradant or stabilising) depending on the nature of the clay (natural or synthetic). However, in absence of oxygen, the PVA and PVA / clay nanocomposites are very photostable. Finally, encapsulation alternating inorganic SiOx layer and PVA or PVA / clay nanocomposite layer permits to obtain the permeability levels required for organic solar cells in niche markets (consumer electronics)

Le Poly Vinyl Alcohol (PVA) a été associé aux verres élaborés dans un système quaternaire (BG) 46S6 par les procédés cités (fusion, sol-gel et sacffolds). Différents paramètres intervenant dans les synthèses des verres bioactifs ont été étudiés, nous citons à titre d’exemple : la température, le pH, la taille des particules, le rapport Polymère / verres, la microstructure, la porosité et la biodégradation. Les caractéristiques thermiques des verres élaborés ont été également déterminées après chaque synthèse par analyse thermique différentielle (DSC/TG, DTA/TG). Ainsi, la température de fusion, la température de transition vitreuse et la température de cristallisation ont été élucidées. Ces caractéristiques thermiques changent lorsque la composition chimique du verre est modifiée. A ce titre, les compositions chimiques ont été étudiées par Fluorescence (XRF) et Inductively Coupled Plasma-Opticale Emission Spectroscopy (ICP-OES) après chaque synthèse pour s’assurer de la pureté des verres bioactifs élaborés et destinés à des applications médicales. Plusieurs techniques physico chimiques d’analyses (DRX, MEB, MET, FT-IR, XRF, ICPOES) ont été mises en oeuvre pour déterminer les propriétés physico chimiques de nos verres bioactifs avant et après expérimentations « in vitro ». Le nano composite Polymère-Verres scaffolds que nous avons obtenu présente des particules de tailles comprises entre 40 et 61 nm et une porosité d’environ 85%. La biodégradation des verres scaffolds décroît lorsque la teneur en verre scaffolds dans le nano composite croît. Les expérimentations « in vitro » montrent qu’après immersion de ces nano composites dans un liquide physiologique synthétique (SBF), une couche d’apatite (phosphate de calcium) se forme à leur surface. L’épaisseur de la couche formée dépend clairement de la taille des particules et du rapport polymère / verre scaffolds
The aim of the present work is the preparation of Bioactive Glass (BG) 46S6 by different techniques. Fabrication of composite scaffolds by using of Poly Vinyl Alcohol (PVA) and quaternary BG (two methods melting and sol-gel) with different ratios to the prepared scaffolds was carried out. Different factor affecting the final properties of the prepared composite scaffolds were investigated in this study, such as; temperature of treatment, BG particle size, polymer/glass ratio, microstructure, porosity, biodegradation, bioactivity, and drug release. The thermal behavior of the prepared bioactive glass by sol-gel and melting techniques were identified using Differential Scanning Calorimetric/Thermo Gravimetric (DSC/TG) or Differential Thermal Analysis/Thermo Gravimetric (DTA /TG). The elemental composition of the prepared bioactive glasses was determined by X-rays Fluorescence (XRF) to confirm that the prepared bioactive glasses have the same elemental compositions and high purity for biomedical applications. The particle size of the prepared bioactive glass was determined by Transmission Electron Microscopic (TEM). Nano-bioactive glass could be obtained by modified sol-gel and the obtained particle size ranged between 40 to 61 nm. The prepared bioactive glass by both applied methods has the same amorphous phase and all identified groups as well as. The porous scaffold has 85% porosity with a slight decrease by increasing the glass contents. The degradation rate decreased by increasing of glass content in the prepared scaffolds. The bioactivity of the prepared composite scaffolds was evaluated by XRD, FTIR, SEM coupled with EDX and Inductively Coupled Plasma-Optical Emission Spectroscopic (ICP-OES). It has been observed that after soaking in Simulated Body Fluid (SBF), there was an apatite layer formed on the surface of the prepared samples with different thickness depending on the glass particle size and polymer/glass ratio

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Removing microcontaminants from effluents is a challenge today, because of its high cost and low efficiency, especially in the treatment of effluents containing heavy metals. An alternative that has emerged is the use of biodegradable nanocomposites, which exhibit good removal and recovery performances, in addition to its low cost. With this in mind, the present study aimed to develop and characterize a nanocomposite based on hydroxyapatite (HAP), polyurethane (PU) and polyvinyl alcohol (PVA) for removing heavy metals. Thus, the research was conducted in several steps: i)- Physico-chemical and microbiological hospital effluent characterization; ii)- Production of hydroxyapatite by aqueous precipitation technique, and their characterization; iii)- Production of the nanocomposite in which the hydroxyapatite was added to the polyurethane prepolymers and then the polyvinyl alcohol/hydroxyapatite film was produced; iv)- Polyvinyl composite without film PU/HAp was also produced in the proportions of 20 and 40% HAp; v)- The composites was characterized by the techniques of XRD, FTIR, SEM / EDS, BET, Zeta Potential and TGA; vi)- The sisal and coconut fibres were washed and dried for comparative tests of adsorption; vii)- Adsorption tests for evaluating the removal of heavy metals (nickel and cadmium). Initial screening adsorption capacity (HAp; PU/HAp - 20 and 40%; PU / HAp / PVA), kinetic studies of adsorption of Cd (II) by HAp; multifactorial design analysis (factorial design) for identifying the most important variables in the adsorption of Cd (II) by composite PU/HAp. Also comparative analysis of adsorption of Cd and Ni by composite PU/HAp were conducted, as well as comparative tests of adsorption of Cd (coconut fibre) and Ni (sisal fibre). It was possible to verify that the composite PU/HAp 40% showed better effectiveness for the removal of Cd (II) and Ni (II), above 80%, equivalent to the lignocellulosic fibre used and HAp produced. As main conclusion, it can be referred that the composite PU/HAp 40% is an effective adsorvent to wastewater treatment for heavy metal removal, with low cost and high efficiency
A remo??o de microcontaminantes, em especial no tratamento de efluentes contendo metais pesados, ? um desafio na atualidade, em decorr?ncia de seu elevado custo e baixa efici?ncia. Uma tecnologia que vem surgindo como promissora ? a aplica??o de nanocomp?sitos biodegrad?veis, a qual apresenta uma efici?ncia favor?vel de remo??o e recupera??o deste microcontaminante, al?m de seu baixo custo. Neste ?mbito, o presente estudo objetivou desenvolver e caracterizar um nanocomp?sito ? base de hidroxiapatita (HAP), poliuretano (PU) e ?lcool povinil?co (PVA) para remo??o de metais pesados. A investiga??o foi desenvolvida em v?rias etapas: i)- caracteriza??o f?sico-qu?mica e microbiol?gica de efluentes hospitalares, como potencial caso de estudo; ii)- produ??o de hidroxiapatita por meio da t?cnica de precipita??o aquosa, e respectiva caracteriza??o; iii)- produ??o de nanocomp?sito com revestimento, no qual a hidroxiapatita (HAp) foi adicionada aos pr?-pol?meros de poliuretano, e a pel?cula de ?lcool poliv?nilico e hidroxiapatita foi produzida e aderida ao comp?sito; iv)- produ??o de comp?sito n?o-peliculado PU/HAp nas propor??es a 20 e 40% de HAp; v)- caracteriza??o do comp?sito pelas t?cnicas de DRX, FTIR, MEV/EDS, BET, Potencial Zeta e TGA; vi)- tratamento f?sico-qu?mico da fibra de sisal e coco, como potenciais bioadsorventes de baixo custo utilizados em estudos comparativos; vii)- testes de adsor??o de metais pesados (n?quel e c?dmio). Neste ?mbito, foi realizada uma triagem inicial de capacidade de adsor??o da HAp, PU/HAp 20 e 40% e PU/HAp/PVA, envolvendo estudos cin?ticos de adsor??o de Cd (II). De modo a identificar as vari?veis mais importantes na adsor??o de Cd (II) pelo comp?sito PU/HAp, foi tamb?m considerado o desenho de experi?ncias (factorial design). Adicionalmente, este adsorvente (PU/HAp) foi tamb?m testado como adsorvente de Cd e Ni. Finalmente, foram realizados testes de adsor??o de Cd em fibras de coco, e de Ni em fibras de sisal. O estudo realizado permitiu concluir que o comp?sito PU/HAp 40% apresentou elevada efici?ncia na remo??o de Cd (II) e Ni (II), superiores a 80%, sendo equivalente ?s fibras lignocelul?sicas utilizadas e ? HAp produzida. Como principal conclus?o deste estudo, destaca-se o fato de que estes materiais podem ser utilizados no tratamento de efluentes para remo??o de metais pesados, dado que apresentam baixo e custo e elevada efici?ncia
2020-01-01

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
O momento atual de maior preocupação ambiental global, a crescente escassez dos recursos fósseis, bem como as novas regulagens ambientais força a busca por materiais que sejam renováveis e compatíveis com o ambiente. Novos materiais estão sendo desenvolvidos a partir de várias fontes naturais e, entre eles a celulose é o mais abundante dos polímeros naturais e um dos mais utilizados. Logo, o objetivo desta dissertação de mestrado foi obter nanofibras de celulose tendo como fonte a fibra vegetal de curauá. Os processos utilizados foram químicos e mecânicos, baseados nos processos de polpação e branqueamento, a fim de isolar a celulose, seguido de processos mecânicos para atingir a escala nanométrica. As nanofibras de celulose propiciam vantagens como melhoria nas propriedades mecânicas e de barreira, além de manter a transparência de polímeros em geral. A fim de comprovar a capacidade de reforço em matrizes poliméricas, as nanofibras de celulose obtidas foram incorporadas nas mesmas. No entanto, para evitar a tendência de aglomeração das nanofibras, principalmente quando retiradas do meio aquoso, o álcool polivinílico (pva) foi escolhido como a matriz polimérica a ser testada, devido à sua compatibilidade com nanofibras de celulose, por ambos serem de natureza hidrofílica, o que aumenta a compatibilidade interfacial de fases entre a nanocelulose e a matriz escolhida. Após a incorporação das nanofibras na matriz polimérica ocorreram significativas melhoras nas propriedades mecânicas da matriz. Ao incorporar 4% de nanofibras da celulose de curauá obteve-se um ganho de 36% e 67% para a tração e para o módulo de young, respectivamente. Com 5% de nanofibras, o aumento nas propriedades foram ainda mais significativos em torno de 44% para a tração máxima e 448% para o módulo de young
Nowadays is a era of greatest environmental concern, with growing scarcity of fossil resources, as well as new environmental regulations obligating the search for materials that are renewable and environmentally friendly. New materials are being developed from various natural sources, and among them, cellulose is the most abundant natural polymers and the one most used. Therefore, the purpose of this thesis was to obtain cellulose nanofibers fibers from curaua plant. The procedures used were based on chemical and mechanical treatment. Pulping and bleaching, in this sequence were done in order to isolate the cellulose, followed by mechanical processes to achieve the nanometer scale. The cellulose nanofibers provide advantages such as improvement of mechanical properties and barrier, besides maintaining transparency of polymers in general. To prove the capacity of reinforcement in polymer matrices, the cellulose nanofibers obtained were incorporated into them. However, to avoid the tendency of nanofibers agglomeration when removed from water, the polyvinyl alcohol (PVA) was chosen as the polymer matrix to be tested, for the reasons that both are hydrophilic in nature and compatible to cellulose nanofibers, which increases the interface between the matrix and the nanocelulose chosen. After the incorporation of nanofibers in the polymer matrix, a significant improvement were observed in its mechanical properties by incorporating 4% of cellulose nanofiber curauá which provided a gain of 36% and 67% for tension and Young's modulus, respectively. With 5% of nanofibers, the increase in properties was even more significant at around 44% for maximum tension and 448% for Young's modulus

Orientador: Alcides Lopes Leão
Banca: Elisabete Frollini
Banca: Pedro de Magalhães Padilha
Resumo: O momento atual de maior preocupação ambiental global, a crescente escassez dos recursos fósseis, bem como as novas regulagens ambientais força a busca por materiais que sejam renováveis e compatíveis com o ambiente. Novos materiais estão sendo desenvolvidos a partir de várias fontes naturais e, entre eles a celulose é o mais abundante dos polímeros naturais e um dos mais utilizados. Logo, o objetivo desta dissertação de mestrado foi obter nanofibras de celulose tendo como fonte a fibra vegetal de curauá. Os processos utilizados foram químicos e mecânicos, baseados nos processos de polpação e branqueamento, a fim de isolar a celulose, seguido de processos mecânicos para atingir a escala nanométrica. As nanofibras de celulose propiciam vantagens como melhoria nas propriedades mecânicas e de barreira, além de manter a transparência de polímeros em geral. A fim de comprovar a capacidade de reforço em matrizes poliméricas, as nanofibras de celulose obtidas foram incorporadas nas mesmas. No entanto, para evitar a tendência de aglomeração das nanofibras, principalmente quando retiradas do meio aquoso, o álcool polivinílico (pva) foi escolhido como a matriz polimérica a ser testada, devido à sua compatibilidade com nanofibras de celulose, por ambos serem de natureza hidrofílica, o que aumenta a compatibilidade interfacial de fases entre a nanocelulose e a matriz escolhida. Após a incorporação das nanofibras na matriz polimérica ocorreram significativas melhoras nas propriedades mecânicas da matriz. Ao incorporar 4% de nanofibras da celulose de curauá obteve-se um ganho de 36% e 67% para a tração e para o módulo de young, respectivamente. Com 5% de nanofibras, o aumento nas propriedades foram ainda mais significativos em torno de 44% para a tração máxima e 448% para o módulo de young
Abstract: Nowadays is a era of greatest environmental concern, with growing scarcity of fossil resources, as well as new environmental regulations obligating the search for materials that are renewable and environmentally friendly. New materials are being developed from various natural sources, and among them, cellulose is the most abundant natural polymers and the one most used. Therefore, the purpose of this thesis was to obtain cellulose nanofibers fibers from curaua plant. The procedures used were based on chemical and mechanical treatment. Pulping and bleaching, in this sequence were done in order to isolate the cellulose, followed by mechanical processes to achieve the nanometer scale. The cellulose nanofibers provide advantages such as improvement of mechanical properties and barrier, besides maintaining transparency of polymers in general. To prove the capacity of reinforcement in polymer matrices, the cellulose nanofibers obtained were incorporated into them. However, to avoid the tendency of nanofibers agglomeration when removed from water, the polyvinyl alcohol (PVA) was chosen as the polymer matrix to be tested, for the reasons that both are hydrophilic in nature and compatible to cellulose nanofibers, which increases the interface between the matrix and the nanocelulose chosen. After the incorporation of nanofibers in the polymer matrix, a significant improvement were observed in its mechanical properties by incorporating 4% of cellulose nanofiber curauá which provided a gain of 36% and 67% for tension and Young's modulus, respectively. With 5% of nanofibers, the increase in properties was even more significant at around 44% for maximum tension and 448% for Young's modulus
Mestre

L’acide polylactique (PLA) est l’un des polymères biosourcés qui suscite le plus d’intérêt, mais ses propriétés thermomécaniques nécessitent d’être améliorées. Pour ce faire, les méthodes les plus utilisées et étudiées sont de le mélanger avec d’autres polymères ou bien d’y ajouter des charges minérales nanométriques (nanoparticules), afin de constituer un nanocomposite à matrice PLA. C’est dans la combinaison de ces deux approches que s’inscrivent ces travaux de thèse, consacrés à l’élaboration et à la caractérisation des propriétés de nanocomposites à base d’un alliage de PLA et de polyamide 11 (PA11) 80/20 m/m. L’objectif de cette thèse est l’obtention d’un matériau biosourcé aux propriétés thermiques, mécaniques et de réaction au feu améliorées par le contrôle de sa morphologie et l’ajout de nanoparticules et de retardateurs de flamme (RF). Pour y parvenir, deux techniques de compatibilisation, destinées à améliorer l’adhésion interfaciale entre le PLA et le PA11, ont été évaluées. La première consistait à incorporer des nanoparticules de silice. Il a été noté d’importantes modifications de la morphologie et des propriétés rhéologiques du mélange d’étude, selon leur localisation dans le mélange étudié fonction de la nature chimique de la surface de la silice. La deuxième consistait à introduire un copolymère époxyde multifonctionnel réactif, dénommé Joncryl. La réactivité de ce copolymère avec le PLA et le PA11 a permis de compatibiliser le mélange d’étude, conduisant à une morphologie plus fine et à l’obtention de propriétés mécaniques supérieures à celles du mélange d’étude, en particulier avec l’ajout de 3%m de Joncryl. Des échantillons basés sur les mélanges compatibilisés par cette méthode ont été préparés par le procédé de fabrication additive FDM. Une étude de l’impact de ce procédé sur la morphologie et les propriétés mécaniques obtenues a été entreprise. Enfin, une meilleure réaction au feu pour le mélange compatibilisé avec 3%m de Joncryl a pu être obtenue par l’ajout combiné de nanoparticules de phyllosilicates et de RF
Polylactic acid (PLA) is one of the biobased polymers that generates the most interest, but its thermomechanical properties need to be improved. To do that, the most used and studied methods consist of blending PLA with other polymers or adding nanoscaled mineral fillers (nanoparticles) to get a PLA based nanocomposite. This PhD work is dedicated to the elaboration and properties characterization of nanocomposites based on a filled PLA and polyamide 11 80/20 wt/wt blend. The aim is to obtain a biobased material with improved thermal, mechanical and fire reaction properties by controlling its morphology through the addition of nanoparticles and flame retardants additives.To achieve that, two compatibilization techniques, aiming to improve PLA-PA11 interfacial adhesion, were evaluated. The first one consisted of adding silica nanoparticles. Important changes of the blend morphology and rheological properties were noticed, depending on the localization of the two different silica nanoparticles used into the polymer blend phases. The second one consisted of introducing a reactive multifunctional epoxy copolymer, named Joncryl. The reactivity of this copolymer with PLA and PA11 allowed to compatibilize the blend, leading to a fine morphology and higher mechanical properties compared to those of the pristine blend. Samples of compatibilized blends obtained through this method were processed using FDM additive manufacturing process. A study of the influence of this process on the morphology and mechanical properties obtained for these samples was performed. Finally, a better fire reaction of compatibilized polymer blend with 3%wt Joncryl was obtained by the combined addition of phyllosilicates nanoparticles and flame retardants

The preparation and characterisation of novel nano-scale biodegradable biocomposite materials, consisting of bacterial cellulose (BC) in a poly(lactic acid) (PLA) matrix, are investigated. BC exhibits high purity, high mechanical strength and an ultra-fine fibrous 3D network structure, while PLA is low cost, biodegradable matrix material derived from natural resources. In this work, composites of BC reinforced PLA were prepared using a solution exchange process and compression molding. The microstructure of the raw materials and composites was characterised using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The thermal properties and crystallinity of PLA and composites were measured using differential scanning calorimetry (DSC). The mechanical properties of pure PLA and composite materials were evaluated using static and dynamic mechanical analysis (DMA). In order to improve the interfacial adhesion between the BC and PLA matrix, BC was acetylated (ABC) or treated with 3-aminopropyltriethoxysilane (APS) coupling agent (SBC). The PLA was plasticized with glycerol (PLAG) in order to increase its ductility. As compared to the Young's modulus of neat PLA (1.9 GPa), ABC generated the highest increase in Young's modulus (4.8 GPa) of the resulting composites followed by BC (4.6 GPa) and SBC (4.5 GPa). The tensile strength of PLA (31 MPa) also was enhanced to 75 MPa with BC, 72 MPa with SBC or 38 MPa with ABC. The ductility of PLAG was degraded with the addition of glycerol. A large amount voids led to a reduction in the mechanical properties of PLAG and PLAG based composites. Every reinforcement led to an improvement in the storage modulus (E') of the neat PLA and PLAG, especially at temperatures above the glass transition temperature (Tg). The DMA results showed that the presence of BC based reinforcements significantly reduced the damping properties of PLA. The reinforcements also influenced the crystalline procedure of PLA. With the addition of BC or ABC to the PLA matrix, the melting points of the composites were increased ~ 4-7 ℃ with a slight change on crystallinity; the crystallinity of SBC-PLA composite decreased from 31.9 % to 26.9 % with only a change of ~ 1 ℃ in the melting point.

Lack of potable water is one of the major challenges that the world faces currently and the effects of this are mainly experienced by people in developing countries. This has therefore propelled research in advanced oxidation technologies AOTs to improve the current water treatment methods using cost effective, non toxic and efficient treatment methods. Hence, in this study the sol-gel synthesis method was used to prepare TiO2 nanoparticles that were photocatalytically active under UV and visible solar light as well as possessing antibacterial properties. Silver and nitrogen doping was carried out to extend the optical absorption of TiO2. For easy removal and reuse of the photocatalyst the nanoparticles were immobilized on chitosan and poly (vinyl-alcohol-co-ethylene) using the electrospining technique. The synthesized nanomaterials were characterized by FTIR, XRD, SEM/EDS, TEM, DRS, and TGA. FTIR and EDS analysis confirmed the formation and composition of TiO2 nanopowders for the doped and undoped nanoparticles. XRD analysis showed that the anatase phase was the dominant crystalline phase of the synthesized nanopowders. SEM and TEM respectively illustrated the distribution and size of the electrospun nanofibers and the nanoparticles of TiO2. DRS results showed that there was a significant shift in the absorption band edge and wavelength of Ag-TiO2 to 397 nm, followed by N-TiO2 at 396 nm compared to the commercial titania which was at 359 nm. The photocatalytic activities and antibacterial properties of these materials were tested on methylene blue dye and E.coli microorganism respectively. Ag-TiO2 immobilized on nanofibers of chitosan and PVAE had the highest photocatalytic activity compared to N-TiO2. Similar results were observed when the biocide properties of these materials were tested on E. coli.

A celulose é o polímero natural renovável disponível em maior abundância atualmente. Por possuir estrutura semicristalina, é possível extrair seus domínios cristalinos através de procedimentos que ataquem sua fase amorfa, como a hidrólise ácida, obtendo-se assim partículas cristalinas chamadas nanopartículas de celulose (NCs). Estas nanopartículas têm atraído enorme interesse científico, uma vez que possuem propriedades mecânicas, como módulo de elasticidade e resistência à tração, semelhantes a várias cargas inorgânicas utilizadas na fabricação de compósitos. Além disso, possuem dimensões nanométricas, o que contribui para menor adição de carga à matriz polimérica, já que possuem maior área de superfície, quando comparadas às cargas micrométricas. Nanocompósitos formados pela adição destas cargas em matrizes poliméricas podem apresentar propriedades comerciais atraentes, como barreira a gases, melhores propriedades térmicas e baixa densidade, quando comparados aos compósitos tradicionais. Como se trata de uma carga com dimensões nanométricas, obtida de fontes renováveis, uma das principais áreas de interesse para aplicação deste reforço é em biopolímeros biodegradáveis. O poli(ácido lático) (PLA), é um exemplo de biopolímero com propriedades mecânicas, térmicas e de processamento superiores a de outros biopolímeros comerciais. No presente trabalho foram obtidas nanopartículas de celulose (NCs), por meio de hidrólise ácida, utilizando-se três métodos distintos, com o objetivo de estudar o método mais eficiente para a obtenção de NCs adequadas à aplicação em compósitos de PLA. Os Métodos I e II empregam extração das NCs por meio do H2SO4, diferenciando-se apenas pela neutralização, a qual envolve diálise ou neutralização com NaHCO3, respectivamente. No Método III a extração das NCs foi realizada com H3PO4. As NCs foram caracterizadas por diferentes técnicas, como difração de raios X (DRX), análise termogravimétrica (TG), espectroscopia vibracional de absorção no infravermelho (FTIR), microscopia eletrônica de transmissão (MET) e microscopia de força atômica (MFA). Os resultados de caracterização das NCs indicaram que, a partir de todos os métodos utilizados, há formação de nanocristais de celulose (NCCs), entretanto, apenas os NCCs obtidos pelos Métodos II e III apresentaram estabilidade térmica suficiente para serem empregados em compósitos preparados por adição da carga no polímero em estado fundido. A incorporação das NCs em matriz de PLA foi realizada em câmara de mistura, com posterior moldagem por prensagem a quente. Compósitos obtidos por adição de NCs obtidas pelo Método II foram caracterizados por calorimetria exploratória diferencial (DSC), análise termogravimétrica, microscopia óptica, análises reológicas e microscopia eletrônica de varredura (MEV). A adição de NCs, extraídas pelo Método II, em matriz de PLA afetou o processo de cristalização do polímero, o qual apresentou maior grau de cristalinidade. Além disso, a adição de 3% em massa de NCs no PLA foi suficiente para alterar seu comportamento reológico. Os resultados reológicos indicaram que a morfologia do compósito é, predominantemente, composta por uma dispersão homogênea e fina da carga na fase matriz. Micrografias obtidas por MEV corroboram os resultados reológicos, mostrando, predominantemente a presença de partículas de NC em escala nanométrica. Compósitos de PLA com NCs obtidas pelo Método III apresentaram aglomerados de partículas de NC em escala micro e milimétrica, ao longo da fase matriz, e não foram extensivamente caracterizados.
Cellulose is the renewable natural polymer currently available in greatest abundance. Cellulose is a semicrystalline polymer, and it is possible to extract its crystalline domains through a procedure that destroys its amorphous phase, such as acid etching, so obtaining crystalline cellulose particles called cellulose nanoparticles (NC). These nanoparticles have attracted great scientific interest because they have mechanical properties similar to those of many inorganic types of filler used in polymer matrix composites, like elastic modulus and tensile strength. Moreover, they have nanometric dimensions, which contribute to lower filler contents in the polymer matrix, due to its increased surface area when compared to the one of micrometric fillers. Nanocomposites formed by adding these fillers into polymeric matrices can present attractive commercial properties such as gas barrier, improved thermal properties, and low density, when compared to traditional composites. As NC are nanometric scale fillers, obtained from renewable sources, there is a great interest in their application into biodegradable biopolymer matrixes. Poly (lactic acid), PLA, is an example of biopolymer that presents improved thermal, mechanical and processing properties, when compared to the ones of other commercial biopolymers. In this work, cellulose nanoparticles (NC) were obtained, via acid hydrolysis, using three different methods, in order to study the most efficient method to obtain NC suitable to be used in polymer matrix composites. NC obtention methods I and II employ extraction by H2SO4. Methods I and II differ only in the neutralization step, which involves dialysis, for Method I, and neutralization with NaHCO3, for Method II. In Method III, the extraction of the NCs was performed using H3PO4. The NC were characterized by different techniques such as X-ray diffraction (XRD), thermogravimetric analysis (TG), infrared absorption spectroscopy (FTIR), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The characterization results indicated that all methods yielded cellulose nanocrystals. However, only NC obtained by methods II and III showed sufficient thermal stability to be used in composites prepared by melt mixing. The NC/PLA composites were prepared in a mixing chamber, followed by hot press molding. The composites with addition of NC obtained by Method II were characterized by differential scanning calorimetry (DSC), TG, optical microscopy, rheological analysis and scanning electron microscopy (SEM). The cellulose nanoparticles extracted by Method II affected the crystallization process of the PLA. The composite presented a higher degree of crystallinity than the pure matrix. Furthermore, the addition of 3 wt% of the NC in PLA was enough to change its rheological behavior. The rheological results indicated that the morphology is predominantly composed by a fine and homogeneous dispersion of the filler in the matrix. The SEM micrographs corroborate the rheological data, showing, predominantly, NC particles in nanometric scale. Composites with NC obtained by Method III presented micro and milimetric scale clusters of NC particles in the matrix phase and were not extensively characterized.

During the past 20 years, a number of aliphatic polyesters have aroused considerable interest due to their biodegradability and biocompatibility, since their use would to reduce the quantity common non-biodegradable polymers (for example PET). In this scenario, studies (both academic and industrial) have been focused on one polymer in particular: polylactic acid (PLA). It is biodegradable, biocompatible and compostable and derives from renewable resources such as corn, potato, cane molasses and beet sugar; it belongs to the family of aliphatic polyesters commonly obtained from α-hydroxy acids which includes other kinds of polymers such as polyglicolic acid or polymandelic acid. PLA was synthesized for the first time by Carothers in 1932 and it was introduced in the market for medical applications at the end of 1960; in the last ten years its good mechanical properties, comparable to those of polystyrene, and an increasing interest for biodegradable polymers have made it interesting for others industrial applications especially in packaging applications as an environmental friendly substitute of traditional plastics. PLA is certainly the most promising and interesting biodegradable polymer for large scale applications for which could be assumed a gradual and progressive replacement of traditional materials coming from hydrocarbon, but there are many aspects such as thermal resistance, impact resistance, gas barrier properties that need to be improved because, at present, are lower than those of traditional polymers. The present PhD project aimed at the synthesis and the study of the properties of new biocompatible polymeric materials based on PLA, focusing the attention on to two main aspects that may have an effect on the final properties of the polymer: the control of the molecular architecture through the use of appropriate chain regulators able to modify the macromolecular structure and he use of nanoparticles, used as such or modified on the surface, added to the polymer matrix. Complex macromolecular architectures give to the materials special properties (for example low melt viscosity, shear sensitivity) that allow the increase of the fields of applications regarding to traditional polymers, while the possibility to use nanometric fillers could represent a new solution in composite materials field; in fact the high surface area of nanoparticle can reduce the amount of fillers added to the polymer improving the properties of the materials even with low percentage of mineral ( 5% w/w). In this work several PLAs with modified macromolecular architecture (star, tree and tree-star) have been synthesized to evaluate the effect of different structure on molecular and rheological properties. Different comonomers have been chosen to obtain complex structures. SEC analyses on samples synthesized with different comonomers show the effect of multifunctional comonomers on the molecular properties of the PLA, especially on the polydispersity index of the system. Star structures show a decrease of polydispersity index, while tree polymers have higher polydispersity than the one of linear PLA. Rheological analyses show the different viscosity of systems having complex macromolecular architectures in comparison with linear PLA. A more complex system is represented by tree-star polymer, obtained using a combination of two or more comonomers; these polymers have a very complex structure, which requires a careful control of feed, allowing to obtain a wide range of PLA with different rheological behavior. The molecular weights and the viscosity of the materials can be modulated changing the comonomers ratio obtaining a wide range of materials with different properties. Nanocomposites with percentages form 0.5% to 5% w/w of different fillers, montomorillonite and nanosilica, have been synthesized. The effects of nanoparticles on molecular properties of PLA are confirmed by the rheological analyses: increasing the amount of fillers complex viscosity decreases, but for low quantity (0.5% and 1% w/w) the viscosity of nanocoposites is higher than pure PLA even if the Mn values are lower. The use of nanoparticles can also modify thermal behavior of PLA; pure PLA has a very slow kinetic of crystallization that leads to a very low tendency of this polymer to form crystals during the cooling phase, therefore the material has an high amorphous phase with a clear and large glass transition. For this reason nanocomposites have been analyzed both with dynamic and in isothermal scanning to study the crystallization process, a very important aspect for the processing and the properties of the polymers, in order to evaluate difference from standard PLA. Nanosilica act as nucleating agent promoting the crystallization process of PLA, while materials containing Cloisite have a large amount of amorphous phase, probably because lamellas are not well separated, and only some samples crystallize during the cooling phase: but anyway the process has very low intensity and is very slow. The surface modification of nanoparticles can reduce the problem caused by the different surface energy between the organic phase (polymer) and the mineral phase (nanoparticle) but can also lead to a variation of material properties. Different organosilanes were used as coupling agents to modify the surface of nanoparticles. Modified nanoparticles were characterized with different techniques to determine both quantitatively and qualitatively the presence of silane on the particle. Titration was used to have quantitative results about the yield of surface modification reaction. Filler-polymer interaction and dispersion of the mineral is improved in presence of the coupling agents, as shown in TEM analysis. The modification of nanoparticles, in particular silica, promotes the crystallization process of the polymer; increasing the amount of silane higher crystallization temperature and crystallization heat are observed and also all crystallization processes are faster in presence of high quantity of silane due to a higher homogeneity of the system. TGA analyses show that all nanoparticles improve thermal stability of PLA. All samples have been synthesized without stabilizers to verify the action of fillers on thermal stability of PLA. The most interesting behavior has been observed in presence of pure silica with a very interesting increase of the degradation temperature. The use of modified silica also decreases the rate of the degradation. PLA nanocomposites have been used to prepare polymeric films by casting to evaluate the permeability of these materials towards different gases, like O2, CO2 and water vapor, in order to evaluate the effect of crystallynity and nanoparticles on this property.

This thesis is about the toughening of poly lactide (PLA). PLA has the potential to be of great importance to the materials world, not only as a solution to address pollution wastes of plastics, but also as a best candidate to be derived from non-petroleum based and renewable resources. The most significant drawback of PLA is its brittleness, which is the focus of the present thesis. Chapter 1 is literature review that focuses mainly on available data on the connections between structure-property relationship of PLA and PLA nanocomposites, and toughening. Chapter 2 entitled: “Improving the Mechanical Properties of Polylactide: Embrittlement or Plasticization?” investigates two conventional methods. These methods are adding nanoclays and plasticizer to control mechanical properties. In Chapter 3, entitled: “Toughening of Polylactide: Single or Hybrid Fillers?” the first steps towards finding a feasible method for improvement in PLA toughness are introduced. The main aim is to improve toughness without sacrificing mechanical properties such as tensile strength and modulus. New ternary PLA nanocomposites introduced in chapter 3 are comprehensively investigated as a main idea in Chapter 4 entitled: “Tensile properties of ternary PLA/EGMA/nanoclay hybrid composites with controlled morphology”. Chapter 5, entitled: “Influence of Phase Microstructure on Mechanical Properties of Ternary Polylactide (PLA) Nanocomposites”, and Chapter 6, entitled: “Effect of Mixing Sequence in the Preparation of PLA/EGMA/Nano-Clay Hybrid Composites” focuses mostly on morphology control. Chapter 7 intends to reach a new milestone for the project. Its main goal is to address one of the most important missing links: “biodegradability”. It is interesting to claim that, for the first time, 100% toughened biodegradable PLA composites has been developed.

Ce travail de thèse se place dans le contexte de la valorisation du polylactide (PLA), un polymère issu de ressources renouvelables, dans le secteur des textiles techniques. Ainsi, de nouveaux filaments nanocomposites ont été élaborés par filage en voie fondue suivi d’un étirage, un procédé facile à mettre en œuvre en milieu industriel et exempt d’utilisation de solvants. Les charges utilisées sont les nanoparticules d’oxyde de zinc (ZnO) et d’argent (Ag) largement utilisées pour apporter des propriétés antibactériennes aux matériaux. De plus, ils sont non toxiques pour les cellules mammifères et assez stables thermiquement pour convenir au procédé de filage en voie fondue. En général les oxydes métalliques (ici le ZnO) sont utilisés pour recycler le PLA par dépolymérisation. Lors de cette étude, différentes techniques ont été utilisées pour le disperser finement dans le PLA et produire des filaments avec une moindre dégradation des propriétés thermo-mécaniques. Ces filaments ont ensuite été utilisés pour réaliser des étoffes maillées qui ont présenté de très bonnes propriétés antibactériennes. Les nanoparticules d’argent à très faible quantité (environ 0,1%) dans le nanocomposites apportent également d’excellentes propriétés antibactériennes. L’incorporation dans le PLA du mélange des deux types de charges (à faible quantité) a conduit à une amélioration significative des propriétés antibactériennes des tricots et ceci après plusieurs lavages. Enfin lors de cette étude, une contribution a été apportée sur l’explication du mécanisme antibactérien du ZnO qui est encore en discussion dans la littérature dans le cas de nos nanocomposites
The objective of this thesis is to valuate polylactide (PLA), a polymer from renewable resources through technical textiles. So new PLA nanocomposite filaments were produced using melt spinning device. This process is solvent free and easy to implement in industry.The fillers used are nanoparticles of zinc oxide (ZnO) and silver (Ag) widely used to provide antibacterial activities to materials and are non-toxic for mammalian cells. Moreover they are thermally stable and suit melt spinning process. Generally metallic oxides (here ZnO) have been used for the recycling of polylactide (PLA) via catalyzed unzipping depolymerization. In this contribution, we used different way to finely dispersed ZnO in PLA and produced filaments with less degradation of thermal and mechanical properties. These filaments are used to produce knitted fabrics with very good antibacterial properties. Silver nanoparticles has also impart excellent antibacterial properties to knitted fabrics with very small amount (around 0,1%). The incorporation of both nanofillers in the PLA improves significantly antibacterial properties of knitted fabrics and allows to obtain very good antibacterial properties even after multiple launderings. Finally, during this study, a contribution was made on the elucidation of the mechanism of antibacterial activity of ZnO still under discussion in the literature in the case our nanocomposite textiles

Orientadores: Ana Rita Morales, Maria Aparecida Marin-Morales
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: Neste estudo, foram preparados nanocompósitos de PLA e argilas organofílicas Cloisite 20A e Cloisite 30B, pelo método de intercalação do fundido. Os materiais foram caracterizados mediante Difração de Raios-X (DRX), Microscopia Eletrônica de Transmissão (MET), Análise Termogravimétrica (TGA) e Calorimetria Diferencial Exploratória (DSC). A influência das argilas organofílicas no processo de biodegradação do PLA foi avaliada pela quantificação da taxa de mineralização do PLA e dos nanocompósitos pela norma ISO 14855-2, em condições simuladas de compostagem. Também foi avaliada a influência das argilas no processo de degradação hidrolítica do PLA, pela análise visual e monitoramento de peso molecular após os períodos de 15 e 30 dias de degradação em composto. Diante da falta de informação relacionada à ecotoxicidade de polímeros biodegradáveis, a avaliação de efeitos citotóxicos, genotóxicos e mutagênicos do composto orgânico após a degradação dos materiais foi realizada empregando o bioensaio com o organismo teste Allium cepa. Os nanocompósitos preparados apresentaram estrutura intercalada, evidenciada pela análise de DRX. As micrografias obtidas por MET permitiram a observação de diferentes níveis de dispersão, incluindo regiões esfoliadas. Foram verificadas, após a incorporação das argilas organofílicas, a redução da estabilidade térmica e o aumento do grau de cristalinidade do PLA, pelas análises de TGA e DSC, respectivamente. Com relação às medidas de mineralização, notou-se que a argila Cloisite 20A não apresentou influência significativa na biodegradação do PLA. Por outro lado, a argila Cloisite 30B levou à redução dos valores de mineralização comparados com o polímero puro, o que pode estar relacionado à atividade antimicrobiana de seu agente modificador. Na avaliação da degradação hidrolítica, notou-se que a presença de argilas organofílicas pode diminuir a taxa de degradação, possivelmente pela atuação de suas camadas como barreira. Ainda assim, mesmo no caso dos nanocompósitos, a redução do peso molecular foi significativa indicando que o processo de compostagem é favorável para a cisão de cadeia do polímero nos materiais em estudo. Na análise realizada por meio do bioensaio com o organismo teste Allium cepa, foi verificado que, após a degradação do PLA e dos nanocompósitos, o composto orgânico apresentou redução do índice mitótico e aumento da indução das alterações cromossômicas, de forma estatisticamente significativa em relação ao controle negativo do ensaio (água destilada). Pela comparação dos resultados obtidos para os nanocompósitos em relação ao polímero puro, não foram verificadas diferenças estatisticamente significativas. Os tipos de aberrações cromossômicas observadas indicam um efeito genotóxico dos materiais, possivelmente relacionado a uma ação aneugênica dos produtos de degradação do PLA
Resumo: Neste estudo, foram preparados nanocompósitos de PLA e argilas organofílicas Cloisite 20A e Cloisite 30B, pelo método de intercalação do fundido. Os materiais foram caracterizados mediante Difração de Raios-X (DRX), Microscopia Eletrônica de Transmissão (MET), Análise Termogravimétrica (TGA) e Calorimetria Diferencial Exploratória (DSC). A influência das argilas organofílicas no processo de biodegradação do PLA foi avaliada pela quantificação da taxa de mineralização do PLA e dos nanocompósitos pela norma ISO 14855-2, em condições simuladas de compostagem. Também foi avaliada a influência das argilas no processo de degradação hidrolítica do PLA, pela análise visual e monitoramento de peso molecular após os períodos de 15 e 30 dias de degradação em composto. Diante da falta de informação relacionada à ecotoxicidade de polímeros biodegradáveis, a avaliação de efeitos citotóxicos, genotóxicos e mutagênicos do composto orgânico após a degradação dos materiais foi realizada empregando o bioensaio com o organismo teste Allium cepa. Os nanocompósitos preparados apresentaram estrutura intercalada, evidenciada pela análise de DRX. As micrografias obtidas por MET permitiram a observação de diferentes níveis de dispersão, incluindo regiões esfoliadas. Foram verificadas, após a incorporação das argilas organofílicas, a redução da estabilidade térmica e o aumento do grau de cristalinidade do PLA, pelas análises de TGA e DSC, respectivamente. Com relação às medidas de mineralização, notou-se que a argila Cloisite 20A não apresentou influência significativa na biodegradação do PLA. Por outro lado, a argila Cloisite 30B levou à redução dos valores de mineralização comparados com o polímero puro, o que pode estar relacionado à atividade antimicrobiana de seu agente modificador. Na avaliação da degradação hidrolítica, notou-se que a presença de argilas organofílicas pode diminuir a taxa de degradação, possivelmente pela atuação de suas camadas como barreira. Ainda assim, mesmo no caso dos nanocompósitos, a redução do peso molecular foi significativa indicando que o processo de compostagem é favorável para a cisão de cadeia do polímero nos materiais em estudo. Na análise realizada por meio do bioensaio com o organismo teste Allium cepa, foi verificado que, após a degradação do PLA e dos nanocompósitos, o composto orgânico apresentou redução do índice mitótico e aumento da indução das alterações cromossômicas, de forma estatisticamente significativa em relação ao controle negativo do ensaio (água destilada). Pela comparação dos resultados obtidos para os nanocompósitos em relação ao polímero puro, não foram verificadas diferenças estatisticamente significativas. Os tipos de aberrações cromossômicas observadas indicam um efeito genotóxico dos materiais, possivelmente relacionado a uma ação aneugênica dos produtos de degradação do PLA
Abstract: In this study, nanocomposites of PLA with organoclays Cloisite 20A and Cloisite 30B were prepared by the melt intercalation method. The materials were characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC). The influence of organoclays in the biodegradation process of PLA was assessed by quantifying the rate of mineralization according to ISO 14855-2, in simulated composting conditions. The influence of clays on the hydrolytic degradation process of PLA was also investigated by visual analysis and monitoring of molecular weight after periods of 15 and 30 days of degradation in organic compost. Given the lack of information related to ecotoxicity of biodegradable polymers, the assessment of citotoxic, genotoxic and mutagenic effects of the organic compost, after the materials degradation, was carried out using the bioassay with Allium cepa as test organism. The nanocomposites presented an intercalated structure, evidenced by XRD analysis. The TEM micrographs allowed the observation of different dispersion levels, including exfoliated regions. After incorporation of organoclays, a reduction of thermal stability and an increasing in the degree of crystallinity of the PLA were observed by TGA and DSC analysis, respectively. In respect to the mineralization, it was noted that the clay Cloisite 20A showed no significant influence on the biodegradation of PLA. On the other hand, the clay Cloisite 30B led to decreased levels of mineralization compared to the polymer, which may be related to an antimicrobial activity of its modifying agent. In the evaluation of hydrolytic degradation it was verified that the presence of organoclays can decrease the rate of degradation possibly by the action of its layers as a barrier. Nevertheless, even in the case of nanocomposites, the molecular weight reduction was significant, indicating that the composting process is favorable to the chain scission of the polymer in the studied materials. In the analysis performed by the bioassay using the test organism Allium cepa, it was verified that after degradation of PLA and the nanocomposites, the organic compost showed an reduction of the mitotic index and an increasing in the induction of chromosomal abnormalities. These results were statistically significant in relation to negative control (distilled water). By comparing the results obtained for the nanocomposites in relation to pure polymer, there were no statistically significant differences. The types of chromosomal aberrations observed indicate a possible genotoxic effect of materials, which may be related to an aneugenic action of the degradation products of PLA
Abstract: In this study, nanocomposites of PLA with organoclays Cloisite 20A and Cloisite 30B were prepared by the melt intercalation method. The materials were characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC). The influence of organoclays in the biodegradation process of PLA was assessed by quantifying the rate of mineralization according to ISO 14855-2, in simulated composting conditions. The influence of clays on the hydrolytic degradation process of PLA was also investigated by visual analysis and monitoring of molecular weight after periods of 15 and 30 days of degradation in organic compost. Given the lack of information related to ecotoxicity of biodegradable polymers, the assessment of citotoxic, genotoxic and mutagenic effects of the organic compost, after the materials degradation, was carried out using the bioassay with Allium cepa as test organism. The nanocomposites presented an intercalated structure, evidenced by XRD analysis. The TEM micrographs allowed the observation of different dispersion levels, including exfoliated regions. After incorporation of organoclays, a reduction of thermal stability and an increasing in the degree of crystallinity of the PLA were observed by TGA and DSC analysis, respectively. In respect to the mineralization, it was noted that the clay Cloisite 20A showed no significant influence on the biodegradation of PLA. On the other hand, the clay Cloisite 30B led to decreased levels of mineralization compared to the polymer, which may be related to an antimicrobial activity of its modifying agent. In the evaluation of hydrolytic degradation it was verified that the presence of organoclays can decrease the rate of degradation possibly by the action of its layers as a barrier. Nevertheless, even in the case of nanocomposites, the molecular weight reduction was significant, indicating that the composting process is favorable to the chain scission of the polymer in the studied materials. In the analysis performed by the bioassay using the test organism Allium cepa, it was verified that after degradation of PLA and the nanocomposites, the organic compost showed an reduction of the mitotic index and an increasing in the induction of chromosomal abnormalities. These results were statistically significant in relation to negative control (distilled water). By comparing the results obtained for the nanocomposites in relation to pure polymer, there were no statistically significant differences. The types of chromosomal aberrations observed indicate a possible genotoxic effect of materials, which may be related to an aneugenic action of the degradation products of PLA
Mestrado
Ciencia e Tecnologia de Materiais
Mestra em Engenharia Química

Poly(lactic acid), (PLA) is a biodegradable and biocompatible polymer which has attracted significant attention as a promising substitute for petroleum-based polymers. To optimize the usage of PLA in a wide range of applications, different methods such as polymer blending and the incorporation of traditional and nanofillers have been extensively explored. Cellulose nanocrystals (CNCs), rod-like nanoparticles with a perfect crystalline structure, are considered as outstanding reinforcing agent owing to the excellent mechanical properties. The optimal characteristics of CNCs as a reinforcing agent in the polymer can be achieved through homogeneous dispersion within the polymeric matrix. However, the strong hydrophilic character of CNCs due to the presence of hydroxyl groups on the surface restricts the uniform dispersion of CNCs in the PLA matrix. In this work, three surface modification treatments along with two different mechanical preparation techniques were employed to improve the dispersion quality of CNCs in the PLA matrix. Polymer adsorption, green esterification, and time-efficient esterification were used as surface modification treatments. Solvent casting and spin-coating method were employed to prepare highly concentrated CNCs masterbatches. Nanocomposites were prepared using melt extrusion, followed by an injection molding process. The morphology of masterbatches indicated better CNCs dispersion through spin-coated thin films, suggesting a high evaporation rate and the effect of centrifugal force and surface tension in the spin-coating process decrease the possibility of CNCs aggregate through the film. Consequently, nanocomposites manufactured using spin-coated masterbatches exhibited higher mechanical strength in comparison with solvent cast ones. In the case of surface modification treatments, the most uniform CNCs dispersion was observed in the nanocomposites reinforced by valeric acid through esterification technique. Higher thermal stability was also achieved through the application of esterification technique. This observation was related to the presence of DMAP on the surface of CNCs which turns into inert materials, prohibiting the thermal degradation. The higher molecular weight and lower molecular number observed in spin-coated samples in comparison with film cast nanocomposites led to the higher damping behavior in spin-coated nanocomposites. This observation indicated the more viscoelastic properties in spin-coated samples owing to the presence of more polymer chain freedom in spin-coated nanocomposites.
National Science Foundation (NSF)
ND EPSCoR (Grant No.11A1355466)

Ce travail de thèse a pour objectif d’élaborer de nouveaux matériaux composites (élastomères, adhésifs) en utilisant les nanocelluloses (NCC et NFC) comme renforts mécaniques biosourcés. Une méthode de fonctionnalisation des nanocelluloses en conditions aqueuses a d’abord été développée, dans le but ultime d’améliorer leur compatibilité avec les matrices polymères. La réaction, basée sur la transestérification des esters de vinyle, a été optimisée à partir de l’acétate de vinyle utilisé comme réactif modèle. Le greffage en conditions basiques s’est avéré efficace, mais a également conduit à la formation de poly(acétate de vinyle) (PVAc) comme produit secondaire. Pour pallier à ce problème, un deuxième protocole en conditions neutres a également été développé, mais des rendements moins bons ont été obtenus dans ce cas. Les nanocelluloses non modifiées et acétylées ont ensuite été dispersés dans une matrice caoutchouc naturel (NR) afin d’étudier l’impact de cette charge sur les performances thermomécaniques du matériau cru ou vulcanisé. Une amélioration des propriétés mécaniques a pu être observée en présence de NCC ou NFC, mais l’acétylation des nanoparticules n’a pas conduit à de meilleures performances. Enfin, une valorisation du PVAc produit lors de l’acétylation des nanocelluloses en conditions aqueuses basiques a été proposée. La dispersion des NCC acétylés dans le PVAc polymérisé in-situ a en effet permis de produire des composites aux propriétés améliorées. L’utilisation ultérieure de ces composites comme charge (mélange-maître) dans des matrices NR ou EVA a été discutée
The objective of this research work consists in the elaboration of novel composite materials (elastomers, adhesives) using nanocelluloses (CNC and NFC) as biobased reinforcing fillers. A method allowing the functionalization of nanocelluloses in aqueous conditions was first developed, with the aim of ultimately improving their compatibility with polymer matrices. The reaction, based on the transesterification of vinyl esters, was optimized with vinyl acetate selected as model reactant. The grafting performed in basic aqueous conditions was efficient, but also led to the formation of poly(vinyl acetate) as a by-product. To limit this problem, a second protocol in neutral aqueous conditions was also developed, but lower yields were obtained in that case. The unmodified and acetylated nanocelluloses were then dispersed in a natural rubber matrix (NR), to study the impact of this filler on the thermomechanical performances of the crude and vulcanized material. An improvement of the mechanical properties was observed in the presence of NCC or NFC, but the acetylation of the nanoparticles did not enhance further the performances. Finally, a valorization of the PVAc produced during the acetylation of the nanocelluloses in basic aqueous conditions was proposed. The dispersion of the acetylated NCC in the PVAc polymerized in-situ indeed led to the production of composites with improved properties. The subsequent utilization of these composites as filler (master batch) in NR or EVA matrices was discussed

Devido à preocupação com o meio ambiente e o volume crescente de resíduos plástico em aterros sanitários, os polímeros biodegradáveis estão sendo estudados extensivamente. Um deles é o PLA. Apesar de possuir propriedades comparáveis a polímeros commodities e polímeros de engenharia, ainda é necessário melhorar certas características do PLA, como resistência ao impacto. Para isso, a nanocelulose (NC) pode ser usada sem alterações significativas na biodegradação polimérica. Este estudo teve como objetivo obter a nanocelulose, caracteriza-la e incorpora-la ao poli(ácido láctico) (PLA), assim como, estudar as propriedades térmicas, morfológicas e mecânicas do compósito obtido. A NC foi obtida por hidrólise ácida utilizando ácido fosfórico e posteriormente foi silanizada com três silanos distintos. As nanopartículas foram caracterizadas por Birrefringência, Microscopia Eletrônica de Transmissão (MET), Termogravimetria (TG), Potencial Zeta, Espectroscopia Vibracional de Absorção no Infravermelho com Transformada de Fourier (FTIR) e Difração de Raio X (DRX). Com as imagens obtidas pelo MET foi possível medir o tamanho das partículas de NC. E então obter a razão de aspecto de 82 e o limite de percolação de 1,1% em massa, confirmando a morfologia de nanofibra. De acordo as analises TG\'s, a presença de NC silanizada aumentou o início da degradação térmica. Os compósitos, contendo 3% em massa de NC, foram obtidos por fusão em câmara de mistura e moldados por injeção. Os compósitos foram caracterizados por FTIR, Cromatografia de Permeação em Gel (GPC), TG, Calorimetria Exploratória Diferencial (DSC), Microscopia Eletrônica de Varredura (MEV-FEG), Impacto e Tração. As análises dos compósitos mostraram que a NC atuou como agente de nucleação, facilitando a cristalização do PLA, além de a NC ter atuado como reforço na matriz polimérica melhorando as propriedades mecânicas.
Due to concern for the environment and the growing volume of plastic waste in landfills, biodegradable polymers are being studied extensively. One of them is the PLA. Despite properties comparable to commodities polymers and engineering polymers, it is still necessary to improve certain characteristics of PLA, such as impact resistance. For this, the nanocelulose (CN) can be used without significant changes on the polymeric biodegradation. This study aimed to obtain nanocelulose, characterizes it and incorporates it to polylactic acid (PLA), even as, studies of thermal, morphological and mechanical properties of the composites processed. The CN was obtained by acid hydrolysis using phosphoric acid and it was, subsequently, silanized with three different silanes. The nanoparticles were characterized by Birefringence, Transmission Electron Microscopy (TEM), Thermogravimetry (TG), Zeta Potential, Spectroscopy Absorption Vibrational Infrared Fourier Transform (FTIR) and X-Ray Diffraction (XRD). By images taken by TEM was possible to measure the size of particles CN. So, obtain the aspect ratio of 82 and the percolation limit of 1.1 wt%, demonstrating morphology of nanofiber. According to TG analysis, the beginning of thermal degradation increased when CN Pure was compared with modified CN. The composite, containing 3 wt% CN, were obtained by melt in mixing chamber and then injection molded. The composites were characterized by FTIR, Gel Permeation Chromatography (GPC), TG, Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), Impact and Tensile Strength. The results showed that the CN acts as a nucleating agent in PLA, facilitating the crystallization and acts as reinforcement in polymer matrix to improve the mechanical properties.

Les nanofibrilles de cellulose (NFC), obtenus par oxydation TEMPO des microfibrilles de cellulose native sous forme de suspensions colloïdales aqueuses, sont des nanoparticules biosourcées ayant des propriétés rhéologiques et optiques particulièrement séduisantes pour la conception de nanomatériaux à haute performance. Le but principal de cette étude était de contrôler et optimiser les conditions de préparation de ces NFCs extraites du rachis de palmier dattier en examinant le temps d'oxydation et le nombre de passe à travers l'homogéinsateur.La réussite de la réaction a été démontrée par spectroscopies FT-IR. Le taux de groupements carboxyliques a été calculé par dosage conductimétrique et était compris entre 221 et 772 µmol/g d'anhydroglucose. Les études morphologiques montrent que NFCs oxydées sont assez bien individualisés grâce à l'introduction des charges négatives à leur surface qui induisent des forces de répulsion électrostatique entre les fibrilles. Une attention particulière a été accordée à la viscoélasticité des suspensions NFC oxydées TEMPO dont le suivi a été réalisé par un rhéomètre ARES-G2TA. Ces nanocharges ont ensuite été incorporées au sein d'un thermoplastique (PVAc), puis les matériaux nanocomposites obtenus ont été caractérisés par MEB, ATG, DSC, DMA et par des tests mécaniques
The cellulose nanofibrils (CNF), obtained by TEMPO oxidation of native cellulose microfibrils as colloidal aqueous suspensions, are biosourced nanoparticles having rheological and optical properties well adapted for the conception of new nanomaterials with high performance.The main purpose of this study was to control and optimize the conditions for preparing these NFCs extracted from date palm tree by examining the oxidation time and the number of passes through the homogenizer..The success of the reaction was demonstrated by FT-IR spectroscopy. The rate of the carboxylic groups has been calculated by conductometric titration and ranged between 221 and 772 mol / g of anhydroglucose. Morphological studies show that oxidized CNFs are very individualized by introducing negative charges on their surfaces that induce electrostatic repulsion forces between the fibrils. Particular attention has been given to the viscoelasticity of oxidized-TEMPO CNF suspensions whose monitoring was carried out by a rheometer ARES-G2TA. These nanocharges were incorporated in a thermoplastic (PVAc) and nanocomposite materials obtained were characterized by SEM, TGA, DSC, DMA and mechanical testing

La fabrication additive est un procédé d’élaboration permettant la mise en forme d’une pièce par ajout de matière, par empilement de couches successives. Bien que de plus en plus de polymères puissent être mis en œuvre par cette technologie, les polymères chargés en sont quasiment absents, alors qu’ils sont largement utilisés dans les autres types de procédés de mise en forme. Les objectifs scientifiques et technologiques du projet concernent (i) une meilleure compréhension des relations entre le comportement rhéologique de systèmes polymères et leur aptitude à la mise en forme par les technologies de fabrication additive FDM, (ii) le développement de formulations de base de polymères bio-sourcés adaptées à ces technologies et apportant une multifonctionnalité. Le premier objectif nécessitera tout d’abord d’identifier les conditions (température, gradients de vitesse, nature des contraintes, …) imposées par les procédés considérés puis de mettre en place et/ou d’adapter les moyens de caractérisation du comportement rhéologique des systèmes polymères dans ces conditions. Le comportement rhéologique en cisaillement mais aussi en élongation pourra être considéré. Il conviendra en particulier d’identifier les compromis nécessaires entre comportement adapté à l’écoulement en filière ou en buse et aptitude à la fusion et à la consolidation couche par couche. Enfin, l’effet des différentes voies de fonctionnalisation envisagées sur le comportement rhéologique et thermique et donc sur l’aptitude à la mise en forme devra être analysé. De façon à adapter les polymères bio-sourcés à un large panel d’applications, diverses voies de fonctionnalisation seront considérées, basées sur le compoundage avec des charges particulaires
Additive manufacturing process is a preparation for the forming of a workpiece by the addition of material, by stacking successive layers. Although more and more polymers can be implemented by this technology, the filled polymers are practically absent, so they are widely used in other types of shaping methods. The scientific and technological objectives of the project are (i) a better understanding of the relationship between the rheological behavior of polymer systems and their ability to shaping by additive manufacturing technologies FDM, (ii) the development of polymer-based formulations biosourced adapted to these technologies and providing multifunctionality. The first goal will require first of all to identify the conditions (temperature, velocity gradients, nature constraints ...) imposed by the processes considered then to implement and / or adapt the means of characterization of the rheological behavior of polymer systems under these conditions. The rheological behavior in shear but also in elongation may be considered. It should in particular identify the necessary compromise between behavior adapted to the flow at the die or nozzle and meltability and consolidation layer by layer. Finally, the effect of different ways of functionalization considered on the rheological and thermal behavior and thus on the ability to formatting will be analyzed. In order to adapt the bio-sourced polymers for a wide range of applications, various routes of functionalization will be considered based on compounding with particulate fillers

Este projeto de mestrado teve como objetivo a obtenção de látices híbridos constituídos de poli(acetato de vinila) (PVAc) e argila montmorilonita (MMT). O homopolímero de acetato de vinila foi sintetizado através da técnica de polimerização em emulsão na presença de diferentes tipos de argila, sendo empregada uma argila sódica (Na-MMT) e três argilas modificadas (o-MMT) com diferentes sais quaternários de amônio. Poli(álcool vinílico) (PVOH) foi utilizado como colóide protetor e persulfato de amônio (APS) como iniciador. Foi estudada a melhor condição para incorporação da argila na matriz polimérica, visando a esfoliação desta nanocarga, resultando desta maneira na formação de nanocompósitos com propriedades diferenciadas. A influência da presença das argilas foi avaliada em termos da velocidade de consumo de monômero, a qual foi acompanhada por gravimetria. Os látices foram caracterizados quanto ao diâmetro médio de partícula e polidispersidade pela técnica de espalhamento de luz (LS). O teor de coágulos do látex foi calculado por análise gravimétrica e a viscosidade analisada em um viscosímetro rotacional. Os filmes nanocompósitos foram caracterizados pelas técnicas de análise dinâmico-mecânica (DMA), análise termogravimétrica (TGA) e difração de raios X (DRX). A morfologia das partículas de látex foi avaliada por microscopia eletrônica de transmissão (MET).
The goal of this project was the preparation of hybrids latexes constituted by poly(vinyl acetate) (PVAc) and montmorillonite (MMT) clays. The poly(vinyl acetate) homopolymer was synthesized via emulsion polymerization in the presence of different types of clay, one sodium clay (Na-MMT) and organically modified clays (o-MMT) with different ammonium quaternary salts. Poly(vinyl alcohol) (PVOH) was used as protective colloid and ammonium persulfate (APS) as initiator. It was evaluated the best condition for the incorporation of the clay in the polymeric matrix, looking forward the exfoliation of the nanofiller, resulting in the formation of nanocomposites with new and improved properties. The influence of clay type and loading was evaluated in terms of latex stability and monomer consumption rate. The latexes were characterized in terms of particle size diameter and polydispersity by light scattering (LS) technique. Coagulum content was determined by gravimetric analysis and viscosity was analyzed in a rotational viscometer. Nanocomposite films were characterized by dynamic-mechanical analysis (DMA), thermogravimetric analysis (TGA) and X-ray diffraction (XRD). Latex particles morphology was evaluated by transmission electron microscopy (TEM).

Este trabalho traz como proposta a obtenção de nanocompósitos (PLA/HDPE-g-AM/HDPE-Verde/n-CaCO3) com propriedades mecânicas e de fluxo adequadas para aplicação no setor de embalagens. A produção desses nanocompósitos ocorreu por meio de uma mistura de PLA e polietileno proveniente de fonte renovável (HDPE-Verde), viabilizada pela ação do agente compatibilizante polietileno enxertado com anidrido maleico (HDPE-g-AM) e do aditivo carbonato de cálcio nanoparticulado (n-CaCO3), através do estudo das condições ótimas de processamento e composição, realizado por meio do Planejamento Fatorial Delineamento Composto Central Rotacional (DCCR). A obtenção deste balanço ótimo se deu ao se avaliar a influência dos fatores de estudo velocidade de rotação (100-400rpm), teor da fase dispersa PLA 2003D (0-35%) e teor da nanocarga mineral - n-CaCO3 (1-4%) sobre as propriedades mecânicas, térmicas, morfológicas e de fluxo dos nanocompósitos, através das variáveis de resposta - módulo de Young, resistência ao impacto, grau de cristalinidade (c) e índice de fluidez (MFI).Avaliações preliminares conduziram à escolha do PLA como fase dispersa dos compósitos. As variáveis de resposta do planejamento indicaram que a viscosidade dessas amostras é diretamente proporcional à concentração de n-CaCO3 e a velocidade de processamento, por promoverem, respectivamente, maior resistência ao escoamento e dispersão da carga. As composições apresentaram como característica resistência ao impacto similar ao comportamento do PLA puro e em contrapartida, módulo de Young similar a matriz de HDPE-Verde. A cristalinidade dos polímeros foi melhorada, observando-se uma ação mútua do HDPE-Verde e do PLA para este aumento, havendo ainda colaboração do n-CaCO3 e da velocidade de mistura. A morfologia dos compósitos foi função da velocidade que favoreceu maior dispersão e distribuição da fase dispersa e ainda por maiores teores de n-CaCO3 que ocasionaram a formação de gotas de PLA de menores dimensões, favorecendo uma estrutura mais homogênea. Maiores teores de PLA alteraram a morfologia dos compósitos, ocasionando a formação de grandes domínios dessa fase na forma de gota que atribuíram ao material maior rigidez. A avaliação individual do efeito do n-CaCO3 sobre o PLA e o HDPE-Verde individualmente apontaram que a ação da carga mineral em geral é benéfica para a melhoria das propriedades, com exceção da resistência ao impacto. Além disso, os resultados mostram que a compatibilizante HDPE-g-AM também minimiza a atuação da carga. Em relação à influência do HDPE-g-AM sobre a mistura HDPE-Verde/PLA é possível observar que a compatibilização da mistura tende a ocorrer, porém não de forma eficiente como o esperado

Mestrado em Engenharia Mecânica
O fabrico aditivo apresenta enorme potencial, uma vez que permite produzir objetos de geometrias complexas muitas vezes sem recorrer a ferramentas auxiliares, sendo ainda capaz de usar uma vasta gama de materiais. Um exemplo de uma das tecnologias aditivas é o fabrico por filamento fundido (FFF), frequentemente associado ao termo "impressão 3D". Um dos materiais termoplásticos mais utilizado é o ácido poliláctico (PLA), um material biocompatível e biodegradável, cuja produção industrial é menos poluente do que a maioria dos termoplásticos presentes no mercado. Com a evolução da tecnologia e uma crescente procura para soluções de impressão 3D, nomeadamente para impressão de peças de dimensões reduzidas e com propriedades específicas, torna-se importante o desenvolvimento de novos materiais. Assim, uma das soluções é a incorporação de nanopartículas, como os nanotubos de carbono e o grafeno, em materiais para impressão 3D, como o PLA. Desta forma, na presente dissertação foi elaborado um plano de trabalho experimental em que se permitiu processar e caracterizar nanocompósitos de PLA com nanotubos de carbono e nanocompósitos de PLA com grafeno. A caracterização mecânica e do índice de fluidez permitiram aferir as propriedades dos nanocompósitos processados e a sua adequação para impressão 3D.
Additive manufacturing has a great potential since it allows the production of objects with complex geometries frequently without resorting auxiliary tools, and still be able to use a wide range of materials. An example is the fused filament fabrication (FFF), frequently associated to "3D printing". One of the most widely used thermoplastics material is polylactic acid (PLA), a biocompatible and biodegradable material, which industrial production is less polluting than most thermoplastics present in the market. With the technology progress and rising demand for 3D printing solutions, especially for small size parts with specific properties, it is important to develop new materials. Thus, one solution is nanoparticles incorporation, such as carbon nanotubes and graphene, in 3D printing materials, such as PLA. In this dissertation was developed an experimental work plan that allowed to process and characterize PLA nanocomposites with carbon nanotubes and PLA nanocomposites with graphene. The processed nanocomposites properties were defined through mechanical and melt flow index characterizations allowing to study their suitability for 3D printing.

Thesis (Ph.D.)--Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Dr. Haskell W. Beckham; Committee Member: Dr. Anselm Griffin; Committee Member: Dr. Johannes Leisen; Committee Member: Dr. Sankar Nair; Committee Member: Dr. Uwe Bunz.

Ce projet vise à développer de nouvelles modifications chimiques de surface des nanocristaux de cellulose (NCC), afin d'améliorer leur compatibilité avec le polymère biosourcé qu'est l'acide polylactique (PLA), afin de combiner leurs propriétés intrinsèques respectives. Ainsi, des matériaux multiphasiques ont été produits à partir de PLA en y incluant des nanomatériaux cellulosiques. L'application visée est celle de l'emballage alimentaire, et l'amélioration des propriétés barrières du PLA, notamment vis-à-vis de l'oxygène et de la vapeur d'eau, est alors un point clé dans la caractérisation des produits finis. Plus précisément, dans ce projet, différentes voies sont proposées pour le greffage de divers composés - polymères ou molécules - à la surface des nanocristaux de cellulose. Le succès de ces greffages a été confirmé et quantifié via diverses techniques de caractérisation. Les NCC ainsi modifiés sont ensuite introduits dans un matériau PLA à travers deux stratégies différentes : soit en tant que nanocharges dans une matrice PLA, avec des taux d'inclusion compris entre 2 et 10% massique, soit en tant que couches internes dans des matériaux multicouches de PLA. Dans les deux cas, les matériaux finaux, préparés à partir de PLA et de nanomatériaux cellulosiques modifiés, présentent des propriétés intéressantes et encourageantes en termes d'homogénéité, de transparence, et de barrière à l'oxygène et à la vapeur d'eau, conformément aux propriétés requises pour les matériaux de conditionnement alimentaire
The purpose of this project is to develop new surface chemical modifications of cellulose nanocrystals (CNCs), in order to enhance their compatibility with biobased poly(lactic acid) (PLA) polymer, and to combine their respective outstanding intrinsic properties. Biobased PLA-based multi-phase materials, including the designed nanostructures, are produced. Furthermore, the final materials are expected to be used in food packaging sector, and the improvement of the barrier properties of the PLA, especially towards oxygen and water vapour, is a key point in the characterization of the materials. In this project, different routes are proposed for the grafting of various compounds - polymers or singles molecules - on the surface of the CNCs. Their grafting efficiency has been confirmed and carefully characterized. The modified CNCs are then introduced in PLA-based materials via two different strategies. Indeed, they are either used as nanofillers in a PLA matrix with inclusion rates comprised between 2 and 10 wt%, or as an inner layer of PLA-based multi-layered materials. In both cases, final PLA-based materials including various designed cellulosic nanomaterials exhibit enhanced and highly encouraging properties in terms of homogeneity, transparency, and barrier towards oxygen and water vapour, in accordance with required properties for food packaging materials

El presente trabajo tiene por objetivo estudiar las aplicaciones de los nanocristales o ¿nanowhiskers¿ extraídos mediante hidrólisis ácida de celulosa bacteriana (BCNW) para el desarrollo de materiales poliméricos y biopoliméricos con propiedades mejoradas para su uso en aplicaciones de envasado de alimentos. En primer lugar se estudió y optimizó el proceso de extracción de BCNW. Se desarrolló un procedimiento de extracción con ácido sulfúrico, que permitió obtener nanocristales con elevada relación de aspecto y cristalinidad y al mismo tiempo, un elevado rendimiento de extracción. Este procedimiento comprende una posterior etapa de neutralización que resultó ser necesaria para garantizar la estabilidad térmica de los nanocristales. El siguiente paso consistió en la formulación de materiales nanocompuestos con propiedades mejoradas incorporando BCNW en diferentes matrices plásticas, en concreto copolímeros de etileno-alcohol vinílico (EVOH), ácido poliláctico (PLA) y polihidroxialcanoatos (PHAs). Mediante las técnicas de electroestirado y estirado por soplado se generaron fibras híbridas de EVOH y PLA con BCNW. La incorporación de BCNW en las disoluciones empleadas para producir fibras modificó significativamente sus propiedades (viscosidad, tensión superficial y conductividad) y por tanto, la morfología de las fibras se vio afectada. Además, se generaron fibras con propiedades antimicrobianas mediante la incorporación de aditivos, maximizando el efecto antimicrobiano con la adición de sustancias de carácter hidrofílico. Seguidamente, se produjeron nanocompuestos por mezclado en fundido y se desarrollaron técnicas de pre-incorporación de BCNW para evitar la aglomeración de los mismos no sólo en matrices hidrofílicas como el EVOH, sino también en matrices hidrofóbicas como el PLA. La dispersión óptima de BCNW resultó en una mejora de las propiedades mecánicas y de barrera de los nanocompuestos. También se estudió la modificación de la superficie de los nanocristales mediante copolimerización con poli(glicidil metacrilato) para mejorar la compatibilidad de BCNW con una matriz hidrofóbica como el PLA. Se incluyen además los primeros resultados obtenidos en cuanto a la producción de nanobiocompuestos sintetizados por microorganismos, que consisten en PHAs con diferentes contenidos de hidroxivalerato reforzados con BCNW. Por último, se desarrollaron películas con propiedades de alta barrera basadas en películas de BCNW recubiertas con capas hidrofóbicas. El recubrimiento mediante la deposición de fibras por electrospinning seguido de homogeneización por calentamiento garantizó una buena adhesión entre las diferentes capas, protegiendo así las películas de BCNW del efecto negativo de la humedad.
Martínez Sanz, M. (2013). Bacterial cellulose nanowhiskers to enhance the properties of plastics and bioplastics of interest in food packaging [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/30312
TESIS
Premiado

碩士
國立海洋大學
食品科學系
91
Nanocomposites of polypropylene (PP)/montmorillonite and poly(vinyl alcohol) (PVA)/montmorillonite were prepared by melt and solution intercalation, respectively. The extent of dispersion of montmorillonite in polymer matrix could be confirmed by X-ray diffraction (XRD). Cetylpyridinium chloride (CPC) was used to modify the montmorillonite, and the interlayer distance was increased to 2.21 nm after the ion exchange with the cation between CPC and montmorillonite. Un-modified montmorillonite mixed with PVA could form intercalated nanocomposite, and exfoliated nanocomposites after the montmorillonite modified by CPC. An intercalated nanocomposite was formed by mixing PVA with 15A montmorillonite, which was less hydrophilic than CPC montmorillonite. PP mixed with montmorillonite did not show intercalation. Both CPC Montmorillonite and 15A montmorillonite blended with PPMA (polypropylene graft maleic anhydride) and PP could form intercalated nanocomposites. The DSC (Differential Scanning Calorimeter) curve of PVA/montmorillonite nanocomposite showed two peaks of heat adsorption. Binding of PVA and montmorillonite exhibited higher melting point than the region where there was no binding.

Graphene, is the building block of many carbon forms, including graphite, carbon nanotubes and Buck-minster fullerenes. It has honey-comb lattice structre with an atomic layer of sp2bonded carbon atoms. Its excellent properties for example, like Youngs modulus is about 1 TPa, breaking strength is about 140 GPa, thermal conductivity is about 5000 Wm-1K-1, and high specific surface area of about 2650 m2g-1.One of the most important application of graphene is in the fabrication of layered polymer nano-composites. Its unique two dimensional morphology provides high available surface area with very small thickness(in nano size) which can be exploited in load bearing, electrical, and barrier applications. However, the reinforcing agents and their types, considerably enhance crystallinity, microstructure, and glass transition of the composites. Therefore, underpinning the processing-microstructure-property relationship in these materials is very important. The easier route of graphene production is through the top-bottom approach, where graphene oxide (GO) is synthesized by chemical exfoliation method followed by suitable reduction of GO to graphene. GO can hold various oxygen containing functional groups that make it easily mixed in nonpolar solvents. Subsequently, by different chemical treatments, few of those functional groups can be removed, and few others can be added/created, and the layer-matrix attachment can be done. The current work focus on the approaches to strengthen the matrix-reinforcement interface by various types of amines, resulting in unbelievably ultra-strong and ultra-tough PVA and PVP nanocomposites. The enhanced mechanical properties were investigated by tensile testing of different graphene oxide samples and chemically reduced graphene samples(reduced by TEA and TEOA).It has been confirmed that the reduced graphene sample shows better elastic properties compare to GO based polymer composites.

碩士
明新科技大學
化學工程研究所
95
This research is divided into two parts. The first part is studied on the preparation of PVA/SiO2 nanocomposite polymers and the second part is studied on the preparation of PE/Al2O3 nanocomposite polymers. For the first part, at the nanoscale of SiO2, owing to the particle size is very small, the surface energy is very higher and easily aggregated when SiO2 dispersed in the PVA. In this research, SiO2 nanoparticles were dispersed in the PVA containing surfactants. The surfactants were used as a disperse agents to improve SiO2 nanoparticles dispersed in the PVA. The properties of PVA/SiO2 nanoparticles polymer films were measured by tensile test, abrasion test and field emission electron probe microanalyzer test. Wendemonstrated the preparation of PVA/SiO2 nanocomposites with improved abrasion increasing 30.5~34.2% compared with PVA. For the second part, Al2O3 nanoparticles were dispersed in the polyethylene(PE) by using laboratory extruder to prepare PE/ Al2O3 nanocomposite polymers. Owing to the Al2O3 nanoparticle is easily aggregated, when dispersed in the PE. Hence, we added Zr-coupling agent to prevent the Al2O3 nanoparticles aggregated when Al2O3 nanoparticle were dispersed in the PE. As a result, we demonstrated there still a little of Al2O3 aggregated when added Zr-coupling agent in the PE/ Al2O3 nanocomposite, therefore the mechanical properties can not be improved, but can be improved the rigidity and abrasion properties.

碩士
中原大學
化學工程研究所
104
Developing a high-performance barrier films attract more attention due to rapid increase of use in food packaging, pharmaceutical, electrical devices, organic materials and metal components. In this study, we fabricated a graphene oxide (GO)/polyvinyl alcohol (PVA) nanocomposite membrane with different cross-linker by solution coating to obtain high water vapor and oxygen barrier film. The role of cross-linker is to provide more stable for final membrane product. Therefore, we studied the effect of cross-linker structure, concentration and cross-linking time on the water vapor barrier performance. ATR-FTIR、XPS、degree of swelling, XRD, thermal Analysis, UV-visible and MOCON data were used to identify the degree of crosslinking, transparency, oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) of the barrier nanocomposite membranes. The results of crosslinker structure, degree of crosslinking and degree of crystallinity will be the major parameters which affect barrier performance of the films at the operating environment is 37。C and 70 RH%. More functional groups and high concentration can increase degree of crosslinking but decrease the degree of crystallinity. Crosslinker with high steric hindrance structure makes the film density decrease. Therefore, the three interactions affect the barrier performance. Using the crosslinker of Tricarballylic acid can obtain the highest degree of crosslinking for crosslinked film and it improve the barrier performance about 27.7%. Crosslinker content for 10 mol% improve the barrier performance about 33.3%. And then increase the crosslinking time to 20 hr. It can improve the barrier performance about 54.3% because it have enough reaction time. So that the crosslinking reaction tends to more completely. Oxygen transmission for crosslinked films on PET substrate are tested at the 37 ° C and 0 RH%. In the study, the crystalline properties of the film dominates the film’s gas barrier properties even if the degree of crosslinking also affect gas barrier properties. High degree of crosslinking decrease the degree of crystallinity, lead to the gas barrier properties decrease. Films maintain the crystalline and partially crosslinked structure which can improve the gas barrier properties. Compared to non-crosslinked film, gas barrier performance increase about 68.5% for the membrane added 5 mol % of tricarballylic acid and crosslinked for 12 hours.

Yes
Poly(vinyl alcohol) (PVA)/graphene oxide (GO) nanocomposite hydrogel as artificial cartilage replacement was prepared via freezing/thawing method by introducing polyethylene glycol (PEG). Efficient grafting of PVA molecules onto GO surface was realized by formation of hydrogen bonding, resulting in exfoliation and uniform distribution of GO in PVA matrix. By introduction of appropriate content of GO, the increased crystalline regions of PVA and the formation of GO centered second network structure led to the increase of the storage modulus and effective cross-linking density. And therefore the mechanical strength and toughness of the composite hydrogel were improved simultaneously: the tensile strength, elongation at break, and compressive modulus showed approximately 200%, 40%, and 100% increase of the neat PVA hydrogel. Besides, for the sample with 1.5 wt % GO content, the maximum force retention and dynamic stiffness were improved remarkably in the process of sinusoidal cyclic compression, and the compressive relaxation stress also increased significantly, indicating the enhancement of the compressive recoverable and antifatigue ability, and resistance to compressive relaxation by formation of high load-bearing, dense, and reinforcing double network structure. Moreover, more than 50% decrease in coefficient of friction was obtained for the composite hydrogel, and the worn surface presented relative smooth and flat features with sharp decreasing furrow depth, confirming the lubrication effect of GO-PEG. This study shows promising potentials in developing new materials for cartilage replacement with simultaneous combination of high mechanical property and excellent lubrication.

碩士
國立臺北科技大學
有機高分子研究所
99
In this study, polyvinyl alcohol (PVA) fibrous membranes with porosity and multi-functions containing nano-silver particles (17.7nm) and coir charcoal powders (332.9nm) was fabricated by electrospinning. The Taguchi method was applied to obtain design parameters for high reproducibility, high quality, high stability, high accuracy, lower processing time and lower cost. In this study, the Experiment is divided into four stages. The first stage, Wet Grinding was applied to obtain coir charcoal powders; the second stage, nano-silver particles was fabricated by Chemical Synthesis Method. These Reinforcements was chosen by granularmetric analysis, UV-Vis spectra analysis, and Transmission Electron Microscopy (TEM). The third stage and the last stage, Taguchi method was applied to design parameters. The PVA/ Coir Charcoal / Nano-Ag Nanocomposite Fibrous Membrane were fabricated by electrospinning. At the same time membrane were surveyed by ATR-FTIR and DSC. Then, functional tests, such as warm test, anti-bacteria test, and Methylene Blue capacity test, was used to obtain the best parameters According to the result of Taguchi Method, the best parameters are that coir charcoals content is 5%, nano-Ag content is 0.5%, operating voltage is 20kV, eletrospinning distance is 15cm. The confirming final experiments were verified by warm test, anti-bacteria test, and Methylene Blue capacity test. The chemical structures of these fibrous membranes were investigated by FT-IR. The surface analysis was observed by SEM. The results of EDS showed the existence of C、O and Ag elements. In terms of Methylene Blue absorption, the Methylene Blue capacity of Optimum membranes is 63.76%. For the warm function, the temperature difference of Optimum membranes is 30.31℃, which is higher than Pure PVA membranes, 21.17℃. As for the effect of antibacterial, the inhibition rate is more than 99%. The thermal properties were analyzed by DSC and TGA which showed the thermal stability is advanced.

Graphene, an atomic layer of sp2 bonded carbon atoms in the hexagonal lattice, is the building block of many carbon forms, including carbon nanotubes, Buckminster Fullerenes, carbon onions, and graphite. Its exceptional properties, for example, Young's modulus of 1 TPa, breaking strength of 140 GPa, thermal conductivity of 5000 Wm-1K-1, and high specific theoretical surface area of 2650 m2g-1, have warranted use in many structural and functional applications. One of the most important uses of it lies as fillers in the fabrication of polymeric nanocomposites. Its special two-dimensional morphology featuring high available surface area with a nanometric thickness of the platelets can be exploited in load bearing, electrical, and barrier applications. However, the reinforcing agents and their types, considerably influence crystallinity, microstructure, and glass transition of the composites, which in turn affect materials properties. Therefore, underpinning the processing-microstructure-property relationship in these materials is of paramount importance. The preferred route of graphene production is through the top-down approach, where graphene oxide (GO) is synthesized by chemical exfoliation method followed by suitable reduction of GO to graphene. GO possesses various oxygen-containing functional groups that make it easily dispersible in aprotic solvents. Subsequently, by various chemical treatments, some of those functional groups can be removed, and few others attached/created, and the filler-matrix interface can be engineered. The crux of the current work lies in the approaches to strengthen the matrix-reinforcement interface by various types of amines, resulting in unprecedented ultrastrong and ultra-tough PVA nanocomposites. Positron annihilation lifetime spectroscopy has been used to highlight the effect of interfaces. X-ray diffractometry and thermal analysis have been used to understand crystallinity in the samples. Raman and FTIR spectroscopy have been used to understand the disorder in carbon and the chemical functional groups, respectively. Microstructural analysis (using scanning and transmission electrons) of matrices and fractured surfaces have been performed to reveal the distribution of fillers, fracture process, formation of nematic crystals, and the in-situ formation of carbon nanoribbons for strengthening. An order of magnitude increase has been found in Young's modulus and fracture strength of the composites. Such profound increase in strength can be ascribed to the nematic ordering of the functionalized GO flakes in the polymer matrix. In another variant, the formation of carbon nanoribbons from the wrinkled GO platelets and their interpenetrating distribution in the polymer matrix led to enhancement in strength and toughness.

碩士
國立成功大學
化學系專班
95
This thesis can be divided into two parts. For the first part, a series of poly(vinyl alcohol)/CaCO3 Nano- composites were prepared. The synthesis principle is first dissolves PVA according to the certain proportion in the water,and Joins the calcium hydroxide, and passes over the carbon dioxide to cause the calcium hydroxide to turn the calcium carbonate. Because the carbon dioxide enters PVA the way to be different, achieves the synthesis calcium carbonate particle size the difference. For the second part, thesis Nanocomposites were subsequently characterized by SEM,Vis-Uv,TGA and tensile force.

碩士
國立高雄師範大學
化學系
101
This research is to synthesize PVA/TMPS/TiO2 nanocomposites with good heat resistance, UV-shielding, high transparency and photocatalytic degradation by sol-gel methods. At the first, the TMPS was performed to the silanol intermediate by hydrolysis in acid solution of pH=2. In order to couple with the organic matrixes the inorganic TiO2 powder was modified by silanol. The active –OH functional groups of TMPS/TiO2 and organic PVA matrixes will progress condensation with each other to synthesize PVA/TMPS/TiO2 nanocomposites. The chemical bonding formation and the best weight contents of reaction components were identified by FT-IR spectra. The thermal resistance, optical transmittance and the ability of photocatalytic degradation, morphology of surface, surface resistance, and hardness of these nanocomposites were measured by TGA, UV-Visible, FE-SEM, super megohmeter and hardness tester respectively. Experimental results showed that these hybrid films had over 90% transmittance and the best Td value of 276.14。C was 20。C higher than the Td value of 256.54。C for PVA. The hardness of these hybrid films was improved from 3H to 6H. The surface resistance of these hybrid films were decreased from 2.15x1010 Ω/cm to 2.13x109 Ω/cm2. The morphology of hybrid films were estimated by FE-SEM. The results of FE-SEM showed that the inorganic TiO2 powder were well distributed throughout the PVA matrixes and the average particles size of these nanocomposites were about 40nm. Finally, the tests of photocatalytic degradation of methylene blue and methyl red with these hybrid films was successful. Keywords: PVA, TiO2, photocatalytic degradation, UV shielding, nanocomposites.

碩士
崑山科技大學
材料工程研究所
99
PLA are used as biomedical materials because they are biodegradable, but the vast majority of biodegradable polymers in clinical use are composed of rather stiff materials that exhibit limited extendibility, weak mechanical strength and poor thermal stability, they are unsuitable for use in numerous applications. We modified PLA with 2-methacryloyloxy- ethyl isocyanate (MOI) to prepare ductile PLA materials. By utilizing the sol-gel process, novel PLA nanocomposites were further prepared with improved thermal stability and mechanical properties. The 10% thermal decomposition temperature for PLA modified with 5% MOI and contained 5-10% silica is 31-36oC higher than that of original pristine PLA. Elongation at break increases by 5-14 times when compared to neat PLA, while the tensile strength maintained at 30-40 MPa. These synthesized PLA nanocomposites can be applied as biomaterials with better mechanical and thermal properties.

碩士
國立雲林科技大學
化學工程與材料工程系
105
In this paper, the purpose of this study is to study the modification of polyvinyl alcohol proton exchange membrane with isocyanate functionalized graphene oxide (GO). The natural graphite was oxidized by Hummer's method to prepare graphene oxide and functionalized graphene oxide with different proportions of 4,4'-diisocyanate dicyclohexylmethane (4,4'-Methylenebis (cyclohexyl isocyanate), HDI). HDI its molecular structure at both ends with an isocyanate (-NCO) functional groups, with hydroxyl and carboxyl reaction, the formation of amide and aminocarboxylic acid, HDI functionalized GO can be divided into three cases: (1) two pieces of GO indirectly on both ends of HDI, (2) HDI at both ends connected to the same GO surface, (3) on the GO surface connected to one end, and the other end -NCO remains unreacted. In order to discuss the difference of modified grafting sites, the functional groups were analyzed by FTIR, and the change of the interlayer distance was observed by XRD. The morphological changes were observed by SEM. Finally, the number of grafts was deduced by EDS element analysis. From the results, the surface of 40 mmol HDI / 1 g GO (iGO40) with the largest number of -NCO functional groups, when the proportion rose to 60mmol HDI / 1g GO (iGO60), the surface with the number of -NCO functional groups But will drop, push the test in the high-quality ratio, will be affected by the molecular structure of the impact of three-dimensional, affecting the graft position. In the PVA / SSA / PSSA-co-MA composite membrane, iGO10, iGO20 and iGO40 were added to the surface isocyanate functional groups, and it was expected that the activation of proton conduction by the interaction between acid and alkali pairs Will be due to esterification reaction, composite film further cross-linking results in the problem of proton conduction decline. The performance of the film was evaluated by proton conductivity, methanol permeability, water content and selectivity. From the results, the interaction between acid and alkali pairs contributes to the increase of proton conduction, and because of the presence of isocyanate functional groups on the surface with hydroxyl groups (-OH) on PVA, the film can be crosslinked to further reduce the methanol infiltration , The highest selectivity was observed at PVA / SSA20 / PSSA-co-MA60 / iGO40 0.5%, the proton conductivity was 23.38 mS / cm, and the methanol permeability was 3.79 × 10-7 cm2 / s.

碩士
國立雲林科技大學
化學工程與材料工程系
107
In this paper, the purpose of this study is to study the modification of polyvinyl alcohol proton exchange membrane with isocyanate functionalized graphene oxide (GO). The natural graphite was oxidized by Hummer's method to prepare graphene oxide and functionalized graphene oxide with different proportions of 4,4'-diisocyanate dicyclohexylmethane (4,4'-Methylenebis (cyclohexyl isocyanate), HDI). HDI its molecular structure at both ends with an isocyanate (-NCO) functional groups, with hydroxyl and carboxyl reaction, the formation of amide and aminocarboxylic acid, HDI functionalized GO can be divided into three cases: (1) two pieces of GO indirectly on both ends of HDI, (2) HDI at both ends connected to the same GO surface, (3) on the GO surface connected to one end, and the other end -NCO remains unreacted. In order to discuss the difference of modified grafting sites, the functional groups were analyzed by FTIR, and the change of the interlayer distance was observed by XRD. The morphological changes were observed by SEM. Finally, the number of grafts was deduced by EDS element analysis. From the results, the surface of 40 mmol HDI / 1 g GO (iGO40) with the largest number of -NCO functional groups, when the proportion rose to 60mmol HDI / 1g GO (iGO60), the surface with the number of -NCO functional groups But will drop, push the test in the high-quality ratio, will be affected by the molecular structure of the impact of three-dimensional, affecting the graft position. In the PVA / SSA / PSSA-co-MA composite membrane, iGO10, iGO20 and iGO40 were added to the surface isocyanate functional groups, and it was expected that the activation of proton conduction by the interaction between acid and alkali pairs Will be due to esterification reaction, composite film further cross-linking results in the problem of proton conduction decline. The performance of the film was evaluated by proton conductivity, methanol permeability, water content and selectivity. From the results, the interaction between acid and alkali pairs contributes to the increase of proton conduction, and because of the presence of isocyanate functional groups on the surface with hydroxyl groups (-OH) on PVA, the film can be crosslinked to further reduce the methanol infiltration , The highest selectivity was observed at PVA / SSA20 / PSSAco-MA60 / iGO40 0.5%, the proton conductivity was 23.38 mS / cm, and the methanol permeability was 3.79 × 10-7 cm2 / s.

Dissertação de mestrado em Técnicas de Caracterização e Análise Química
Poly(lactic acid) (PLA) is a biodegradable aliphatic thermoplastic polyester well known for being a promising alternative to petroleum-based materials as it can be produced from renewable resources at low cost and recyclable to its monomer. Although this polymer has good properties compared to other biodegradable polymers, it presents some limitations, like poor thermal and mechanical resistance and limited gas barrier properties. The incorporation of nanoclays has been used as a way to overcome this problem. Since resistance to UV light is a key factor for polymeric materials used in outdoor applications, it is important to investigate the effect of these nanoparticles. Thus, the present work aims to investigate the influence of clay type (Cloisite 30B, Cloisite 15A and Dellite 43B) and amount (3 and 5 wt.%) on PLA thermal and UV stability. PLA and PLA nanocomposites prepared by melt mixing were submitted to thermo-­oxidative degradation during 120 hours and exposure to UV light in an accelerated chamber for 600 hours. Starting materials and samples removed along the degradation time were characterized by solution viscosimetry, energy-­dispersive spectroscopy (EDS), scanning electron microscopy (SEM), X-­ray diffraction (XRD), proton nuclear magnetic resonance (1H-­NMR), Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TGA) and differential scanning calorimetry (DSC). The prepared nanocomposites exhibited intercalated structure. However, the presence of nanoclay aggregates was detected in C15A nanocomposites. Even though after thermo-­oxidative degradation all samples exhibited a significant decrease in intrinsic viscosity, it was minor for nanocomposites containing 3 wt.% nanoclays. An increase in the crystallinity degree was also observed for degraded nanocomposites. UV ageing results showed that the presence of nanoclays in PLA matrix induces polymer photo-­degradation, as higher decrease of intrinsic viscosity and changes in chemical structure were observed. FTIR spectra of degraded C30B nanocomposites indicate that anhydride groups are formed during photo-­degradation. PLA nanocomposites prepared in the present work exhibited higher thermal stability and lower photo stability than PLA.
O ácido poli-­láctico (PLA) é um poliéster alifático biodegradável conhecido por ser um promissor substituto de materiais derivados de petróleo, uma vez que pode ser produzido a partir de recursos renováveis de baixo custo e reciclável até à obtenção do monómero. Embora este polímero apresente boas propriedades, quando comparado com outros polímeros biodegradáveis, também apresenta algumas limitações como baixa resistência térmica e mecânica e propriedades de barreira limitadas. A incorporação de nanoargilas em PLA tem sido utilizada como forma de ultrapassar estas limitações. No entanto, como a resistência à radiação é um fator chave nos materiais poliméricos quando utilizados em aplicações exteriores, é necessário investigar o efeito destas nanopartículas. Assim, o presente trabalho tem como objetivo investigar a influência do tipo de nanoargila (Cloisite 30B, Cloisite 15A e Dellite 43B) e quantidade (3 e 5 %) na estabilidade térmica e UV do PLA. Os nanocompósitos de PLA foram submetidos a 120 horas de degradação termo-­oxidativa e a 600 horas de exposição à radiação UV numa câmara de degradação acelerada. Os materiais iniciais e amostras retiradas ao longo do tempo foram caracterizados através de viscosidade de soluções, espetroscopia de dispersão de energia de raios-­X (EDS), microscopia eletrónica de varrimento (SEM), difração de raios-­X (XRD), espetroscopia de infravermelho com transformadas de Fourier (FTIR), termogravimetria (TGA) e calorimetria diferencial de varrimento (DSC). A caracterização das amostras iniciais mostrou que se obtiveram nanocompósitos com estrutura intercalada, mas com a nanoargila C15A verificou-­se a presença de agregados. Após degradação termo-­oxidativa, todas as amostras exibiram uma diminuição da viscosidade intrínseca, que foi menos acentuada no caso dos nanocompósitos com adição de 3% de nanoargila. Verificou-­se ainda um aumento da cristalinidade nas amostras degradadas. Nas amostras expostas à radiação UV constatou-­se que a presença de nanoargilas induziu a foto-­degradação do PLA, uma vez que ocorreu maior diminuição de viscosidade intrínseca e maiores alterações na estrutura química. Os espectros de FTIR dos nanocompósitos com C30B evidenciaram a formação de grupos anidrido durante a degradação. Os nanocompósitos de PLA preparados neste trabalho apresentam maior estabilidade térmica e menor estabilidade à radiação UV que o PLA.

Poly (lactic acid) (PLA) is a promising substitute for conventional petroleum-based polymer materials as a result of its environmentally benign quality and suitable physical properties. However, there are also problems associated with properties, such as brittleness, low heat deflection temperature, low melt viscosity, as well as cost that prevent wide-range applications of PLA This work reports on melt extrusion preparation of PLA/clay/wood nanocomposites involving various compatibilizers, resulting in remarkable improvements in mechanical as well as in thermal material properties. In particular, the tensile and flexural moduli of PLA/clay/wood nanocomposites with 30 wt. % wood flour and 5 wt. % nanoclay respectively increased from 3.75 to 7.08 GPa and from 3.83 to 6.01 GPa compared to neat PLA. The thermal decomposition temperature improved by about 10°C compared to that of PLA/wood composites A mathematical model was developed based on Eshelby's equivalent inclusion method and Mori-Tanaka's background analysis to successfully predict longitudinal elastic moduli of complex structured nanocomposite materials
acase@tulane.edu

碩士
萬能科技大學
材料科技研究所
99
In this study, montmorillonite clay was modified with NH4Cl and then exfoliated or intercalated the structures in a polylactic acid (PLA) martix by torque rheometer in the ratio of 0.5 wt %、3.0 wt %、5.0 wt %、8.0 wt %. X-ray diffraction (XRD) revealed that modified MMT was distributed successfully in the PLA matrix. And by TEM that the 3.0wt% OMMT dispersed in the PLA is also more uniform best. After thermal pressing, we used TGA to examine the thermal resistance of the resulting composites, co-rotating twin screw extruder palletizing system to blend OMMT and PLA, then injected following specification of ASTM-D638 to form standard specimen to measure the material strength by MTS. We found that the mixture of organophilic clay and PLA enhanced the thermal stability. The best one is PLA/3wt% OMMT nanocomposite, the TGA maximum decomposition temperature (Tmax) rise from 336.84 °C to 339.08 °C and 5 wt% loss temperature rise from 325.14 °C to 326.48°C. No degradation of water Breaking elongation ratio before the maximum elongation (10.19%); tensile strength of 58.00 MPa, maintained by the week for the 28.18MPa degradation. A blending of quantitative OMMT after (≧3.0wt%), including its mechanical properties, breaking elongation ratio, tensile strength, breaking strength Dengjun in almost two weeks after the value of the minimum, that the right amount of OMMT can greatly enhance its degradation rate of water. After progressing the vibrating hydrolysis reaction of PLA/OMMT nanocomposites, we used DSC to study the difference between before and after hydrolysis of the resulting composites. The results of DSC revealed that OMMT blending help hydrolytic degradation of PLA, and make Tg, Tc , and Tm1 decreased.

Biobased polymers are a critical research topic as they may serve as replacement to traditional unsustainable petro-chemical polymers. It is vital to widen its range of applications by improving its physical and mechanical properties via light weighting and strength improvements. Light weighting can be accomplished by introducing foam morphology to the material while mechanical strength improvements can be achieved by inserting stiff filler material to the base polymer to form a composite. This study explores the physical, mechanical, thermal, rheological and morphological properties of blends, foams and composites between biobased PLA and PHBV matrix polymers and biobased chitin nanowhisker filler. It was found that foams produced from PLA and PHBV blends exhibits refined cellular morphology which leads to light weighting and good strength preservation while chitin nanowhiskers was determined to be a very effective filler for mechanical property improvements in both solid and porous materials.

碩士
輔仁大學
化學系
95
Abstract A high dielectric constant composite of polyaniline,PANI-DBSA/PAA has been synthesized by using the technique of in-situ polymerization of aniline in a aqueous dispersion of poly(acrylic acid) (PAA) in the presence of dodecylbenzene sulfonate (DBSA). The water-soluble PAA serves as a polymeric stabilizer which can protect the PANI particles from macroscopic aggregation . SEM micrograph reveals that the composite prepared consists of numerous nano-scale (~70nm) PANI particles evenly distributed within the PAA matrix . A high dielectric constant value of ca. 105(at 1 kHZ ) was obtained by the composite containing 20 wt% of PANI . The high dielectric constants of these composites are attributed to the accumulation of the tiny capacitors formed by PANI nano particles . The influences of PANI and water contents on various properties such as morphological ,thermal dielectric and electrical behaviors were investigated . On the other hand ,these composites exhibit high dielectric loss due the conductive nature of the PANI particles , especially when PANI content in the composite is high.

碩士
輔仁大學
食品科學系
99
Incorporation of nano-filler into polyolefin structure has been widely used in current packaging development for better performance, such greater barrier and mechanical properties. The objectives of this study focused on the preparation and characterization of nanocomposite made of PLA and chitosan nanoparticles. Particle sizes of chitosan were ranging 5~10 μm, and were reduced nano scale by homogenizer; however, chitosan particles clustered to micrometers after standstill for hrs. Use of Tween-80 in an acidic chitosan solution resulted to sustain the particles ranging nano-scale after nanorization. Addition of 0.4% chitosan to PLA led to the surface structure of the nanocomposite film more inseparable determined by polarizing microscope. Glass transition temperatures (Tg) of the nanocromposite films were from 57.8 o C rising to 149.2 o C in the presence of 0.4% chitosan. The addition of chitosan also modified the mechanical properties of nanocomposite films, that the tensile strength significant decreased with 0.4% chitosan added, and the tensile strength dropped from 231.34 MPa to 211.32 MPa. Moreover, the tensile strength of PLA/chitosan was still greater than PLA/clay composite films. Added 0.1% chitosan would decrease the elongation from 12.4% to 6.88%. On the other hand, high negative correlation between tensile strength and elongation was observed. Conclusively, incorporation of chitosan nanoparticles into PLA microstructure is beneficial to greater crystallinity and thermal stability, which may optimize its applications. Keywords: nanotechnology, biodegradable, polylactide, chitosan

碩士
國立臺北科技大學
有機高分子研究所
104
In this study, the PAA/clay nanocomposites and PAN/clay nanocomposites were prepared by in-situ polymerization. In the research, the first part was synthesized modifier (4-(N,N-Diethyldithiocarbamylmethyl)benzyltrimethylammonium Bromide) which is the RAFT regant helping monomer to polymerize.Sencond part was preparing nanocomposites. We modified Montomorilloite (C34P5 and CloisiteNa+) by modifier, then adding monomer to do in-situ polymerization. We try to use higher content(about 30%) of clay and use the instrument of XRD and FT-IR to identify the structure and the distance between layered silicate of production. Also we used FT-IR and NMR to identify whether the modifier (4-(N,N-Diethyldithiocarbamylmethyl)benzyltrimethylammonium Bromide) was synthesized successfully or not. In the study, we hope to find better formula and condition to prepare PAA,PAN/nanocomposite.

碩士
淡江大學
化學工程與材料工程學系碩士班
98
Biodegradable polymers have recently attracted great attension because environmental pollution. PLA is a aliphatic thermoplastic polyester and a biodegradation plastic. In this study, we use hydrophobic intercalation agent (POP-diamine) to ezpansion the inter-lamellar space of Na+-MMT. We hope it could increase the disperse of montmorillonite. Then we measure the physical properties and mechanical properties, and compare with commercial modified montmorillonite (C30B).Finally, we degrade the PLA nanocomposites by streptomyces 76T-1 to investigate the degradability of PLA nanocomposites. We could expand the inter-lamellar space from 1.24 nm to 4.64 nm by using POP-diamine as intercalation agent. But after meting blending, the inter-lamellar space would reduce to 2.26 nm. The reason is the POP-diamine would move to PLA matrix after melting blending. We could prepare intercalation-nanocomposite by melting blending with C30B. When adding C30B, we could increase the modulus of PLA.And when adding the POP-MMT, we could increase the elonation at break. By adding the montmorillonite, we could increase the thermal ability of PLA. We use Streptomyces sp. 76T-1 to degrade PLA. After degradating test in 72 hour, PLA could be degradating completely. Adding cloisite 30B could accelerate the degradating rate. But POP-diamine could slow down the degradating rate. After degradating test in 72 hour, we still have 40%wt PLA. After degradating test, we found that the crystallinity and molecular weight have not changing. For understanding the relation between degradation rate and crstallinity, we made hight crystallinity PLA (crystalinity 37 %). After degradating test in 72 hour, we still have 80 wt% PLA. In the result of SEM, we found that Streptomyces sp. 76T-1 degrade the amorphous firstly, then crystalline. By the results of thickness test and molecular weight test in this paper, we assume that Streptomyces sp. 76T-1 degrade PLA by surface erosion.